104 results on '"Markus Andreas Schubert"'
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2. Room Temperature Light Emission from Superatom-like Ge–Core/Si–Shell Quantum Dots
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Katsunori Makihara, Yuji Yamamoto, Yuki Imai, Noriyuki Taoka, Markus Andreas Schubert, Bernd Tillack, and Seiichi Miyazaki
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Si quantum dots ,core/shell structure ,CVD ,Chemistry ,QD1-999 - Abstract
We have demonstrated the high–density formation of super–atom–like Si quantum dots with Ge–core on ultrathin SiO2 with control of high–selective chemical–vapor deposition and applied them to an active layer of light–emitting diodes (LEDs). Through luminescence measurements, we have reported characteristics carrier confinement and recombination properties in the Ge–core, reflecting the type II energy band discontinuity between the Si–clad and Ge–core. Additionally, under forward bias conditions over a threshold bias for LEDs, electroluminescence becomes observable at room temperature in the near–infrared region and is attributed to radiative recombination between quantized states in the Ge–core with a deep potential well for holes caused by electron/hole simultaneous injection from the gate and substrate, respectively. The results will lead to the development of Si–based light–emitting devices that are highly compatible with Si–ultra–large–scale integration processing, which has been believed to have extreme difficulty in realizing silicon photonics.
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- 2023
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3. Towards the Growth of Hexagonal Boron Nitride on Ge(001)/Si Substrates by Chemical Vapor Deposition
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Max Franck, Jaroslaw Dabrowski, Markus Andreas Schubert, Christian Wenger, and Mindaugas Lukosius
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hexagonal boron nitride ,2D materials ,chemical vapor deposition ,DFT ,borazine ,Chemistry ,QD1-999 - Abstract
The growth of hexagonal boron nitride (hBN) on epitaxial Ge(001)/Si substrates via high-vacuum chemical vapor deposition from borazine is investigated for the first time in a systematic manner. The influences of the process pressure and growth temperature in the range of 10−7–10−3 mbar and 900–980 °C, respectively, are evaluated with respect to morphology, growth rate, and crystalline quality of the hBN films. At 900 °C, nanocrystalline hBN films with a lateral crystallite size of ~2–3 nm are obtained and confirmed by high-resolution transmission electron microscopy images. X-ray photoelectron spectroscopy confirms an atomic N:B ratio of 1 ± 0.1. A three-dimensional growth mode is observed by atomic force microscopy. Increasing the process pressure in the reactor mainly affects the growth rate, with only slight effects on crystalline quality and none on the principle growth mode. Growth of hBN at 980 °C increases the average crystallite size and leads to the formation of 3–10 well-oriented, vertically stacked layers of hBN on the Ge surface. Exploratory ab initio density functional theory simulations indicate that hBN edges are saturated by hydrogen, and it is proposed that partial de-saturation by H radicals produced on hot parts of the set-up is responsible for the growth.
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- 2022
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4. Operando diagnostic detection of interfacial oxygen ‘breathing’ of resistive random access memory by bulk-sensitive hard X-ray photoelectron spectroscopy
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Gang Niu, Pauline Calka, Peng Huang, Sankaramangalam Ulhas Sharath, Stefan Petzold, Andrei Gloskovskii, Karol Fröhlich, Yudi Zhao, Jinfeng Kang, Markus Andreas Schubert, Florian Bärwolf, Wei Ren, Zuo-Guang Ye, Eduardo Perez, Christian Wenger, Lambert Alff, and Thomas Schroeder
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HAXPES ,resistive switching ,interface ,RRAM ,HfO2 ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
The HfO2-based resistive random access memory (RRAM) is one of the most promising candidates for non-volatile memory applications. The detection and examination of the dynamic behavior of oxygen ions/vacancies are crucial to deeply understand the microscopic physical nature of the resistive switching (RS) behavior. By using synchrotron radiation based, non-destructive and bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES), we demonstrate an operando diagnostic detection of the oxygen ‘breathing’ behavior at the oxide/metal interface, namely, oxygen migration between HfO2 and TiN during different RS periods. The results highlight the significance of oxide/metal interfaces in RRAM, even in filament-type devices.
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- 2019
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5. One-Transistor-Multiple-RRAM Cells for Energy-Efficient In-Memory Computing.
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Max Uhlmann, Emilio Pérez-Bosch Quesada, Markus Fritscher, Eduardo Pérez, Markus Andreas Schubert, Marc Reichenbach, Philip Ostrovskyy, Christian Wenger, and Gerhard Kahmen
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- 2023
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6. Titanium Nitride Plasmonic Nanohole Arrays for CMOS-Compatible Integrated Refractive Index Sensing: Influence of Layer Thickness on Optical Properties
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Sebastian Reiter, Weijia Han, Christian Mai, Davide Spirito, Josmy Jose, Marvin Zöllner, Oksana Fursenko, Markus Andreas Schubert, Ivo Stemmler, Christian Wenger, and Inga Anita Fischer
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Biophysics ,Biochemistry ,Biotechnology - Abstract
The combination of nanohole arrays with photodetectors can be a strategy for the large-scale fabrication of miniaturized and cost-effective refractive index sensors on the Si platform. However, complementary metal–oxide–semiconductor (CMOS) fabrication processes place restrictions in particular on the material that can be used for the fabrication of the structures. Here, we focus on using the CMOS compatible transition metal nitride Titanium Nitride (TiN) for the fabrication of nanohole arrays (NHAs). We investigate the optical properties of TiN NHAs with different TiN thicknesses (50 nm, 100 nm, and 150 nm) fabricated using high-precision industrial processes for possible applications in integrated, plasmonic refractive index sensors. Reflectance measurements show pronounced Fano-shaped resonances, with resonance wavelengths between 950 and 1200 nm, that can be attributed to extraordinary optical transmission (EOT) through the NHAs. Using the measured material permittivity as an input, the measured spectra are reproduced by simulations with a large degree of accuracy: Simulated and measured resonance wavelengths deviate by less than 10 nm, with an average deviation of 4 nm observed at incidence angles of 30° and 40°. Our experimental results demonstrate that an increase in the thickness of the TiN layer from 50 to 150 nm leads to a sensitivity increase from 614.5 nm/RIU to 765.4 nm/RIU, which we attribute to a stronger coupling between individual LSPRs at the hole edges with spatially extended SPPs. Our results can be used to increase the performance of TiN NHAs for applications in on-chip plasmonic refractive index sensors.
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- 2023
7. High Quality Ge Growth on Si (111) and Si (110) by Using Reduced Pressure Chemical Vapor Deposition
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Yuji Yamamoto, Wei-Chen Wen, Markus Andreas Schubert, Cedic Corley-Wiciak, and Bernd Tillack
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Heteroepitaxial growth of Ge on Si has great interest for various optoelectronic applications such as Ge photodiodes(1). However 4.2% of lattice mismatch causes dislocation formation and island growth. High quality Ge(001) growth techniques are reported in ref.(2-4). Moreover, Ge(111) surface is also interesting because of higher carrier mobility(5). Furthermore, Ge(110) is preferred orientation of virtual substrates for epitaxial graphene growth(6). In the case of the Ge deposition on Si(111) and Si(110) substrates, it seems that the process conditions used for Ge growth on Si(001) are not suitable to realize high crystallinity and smooth surface (7). In this paper, we present a method of high quality and smooth Ge layer growth on Si(111) and Si(110), which is the same level as the Ge growth on Si(001). Epitaxial growth of Ge on Si(111) and Si(110) is carried out using a reduced pressure chemical vapor deposition system. After HF last clean, a wafer is baked at 1000°C and cooled down to 600°C in H2 and further to 300-550°C in N2 to form a hydrogen-free Si surface. Then a 100 nm thick Ge layer is deposited as a seed layer using GeH4 with N2 carrier gas. Afterward the wafer is heated up to 450-650°C in H2 and the main part of Ge is deposited using a H2-GeH4 gas mixture. For threading dislocation density (TDD) reduction, annealing at 800°C in H2 is performed for several times (cyclic annealing) by interrupting the Ge growth. Atomic-force microscopy (AFM) is used for surface roughness analysis. Scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD) are used for structural characterization of the Ge layer. Secco defect etching combined with angle view scanning electron microscopy (SEM) or optical microscope is used for TDD evaluation. Figure 1(a,b) summarize the root mean square (RMS) roughness of Ge(111) and Ge(110) seed layers grown at 300-550°C before and after postannealing at 600-800°C. If the growth temperature is lower than 350°C for Ge(111) and 400°C for Ge(110), a significant increase of the surface roughness is observed after postannealing at 700°C and 800°C, respectively. For both crystal orientations, the lowest RMS roughness is observed by depositing at 450°C for as deposited and postannealed samples. The maintained RMS roughness even after postannealing at 800oC may be indicating good crystal quality even at as deposited condition. To confirm the influence of the growth temperature on the crystallinity, cross section TEM images of the Ge(111) and the Ge(110) seed layers deposited at 300°C and 450°C are shown in Fig. 2(a-d). In the case of Ge growth at 300°C (Fig. 2(a,b)), a very high density of stacking faults (SF) and high surface roughness are observed for both crystal orientations. In contrast, by depositing at 450°C (Fig. 2(c,d)), lower SF density in the Ge layer is observed compared to that at 300°C. By postannealing, an improvement of crystallinity is observed for the Ge seed layers deposited at 450°C. However, in the case of 300°C, the crystallinity cannot be improved by the postannealing, because a too high density of dislocations and SF may cause irregular Ge atom migration. As the result, surface roughening occurs. Figure 3(a,b) show AFM surface roughness images after 5 μm-thick Ge(111) and Ge(110) deposited with cyclic annealing at 800°C, respectively. Clear terraces of ~0.3 and ~0.2 nm, whose heights are close to those of Ge(111) bilayer and Ge(110) monolayer, are observed, respectively. RMS roughness of the Ge(111) and the Ge(110) are 0.51 and 0.35 nm, respectively. These RMS roughnesses are comparable to a level reported for Ge (001) in ref.(1). Figure 4 shows TDD of Ge(111) and Ge(110) surfaces as a function of the Ge thickness deposited with cyclic annealing on Si(111) and Si(110) substrates. For both orientations, TDD of ~4×108 cm-2 is obtained for 500 nm-thick samples. With increasing the Ge thickness, the TDD is reduced and levels below TDD of ~5×106 cm-2 are achieved for both Ge (111) and Ge(110) for 5 μm-thick Ge. These methods enable high quality virtual substrate fabrication not only for (001) surfaces but also for (111) and (110) orientation without a chemical mechanical polishing process. References Lischke et al. Nature Photonics15 (2021) 925 Yamamoto et al. Solid-State Electron. 60 (2010) 2 Yamamoto et al. Semicond. Sci. Technol. 33 (2018) 124007 M. Hartmann et al. J. Appl. Phys. 95 (2004) 5905 H. Lee et al. IEDM Tech. Digest (2009) 09-457 J-H. Lee et al. Science 344 6181(2014) 286 M. Hartmann et al. J. Cryst. Growth 310 (2008) 5287 Figure 1
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- 2022
8. 3-Dimensional Self-Ordered Multilayered Ge Nanodots on SiGe
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Wei-Chen Wen, Markus Andreas Schubert, Marvin Hartwig Zöllner, Bernd Tillack, and Yuji Yamamoto
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Multilayered Ge nanodots have drawn much attention due to their potential applications in optoelectronics, such as photodetectors and lasers. Many groups studied multilayered Ge nanodots with Si spacers on Si(001) grown by Stranski-Krastanov (SK) growth mode and vertically aligned by local tensile strain induced by buried Ge nanodots (1-2). However, to avoid plastic relaxation caused by a 4.2% lattice mismatch between Si and Ge, thick nanodots and/or large layer numbers are challenging. Additionally, laterally-aligned Ge nanodots without pre-structuring have not been reported. In this study, we demonstrate 3-dimensional (3D) self-ordered Ge nanodots on SiGe virtual substrate (VS) by SiGe/Ge cyclic epitaxial growth and show the effects of fabrication parameters. The 3D self-ordered Ge nanodots were fabricated by reduced-pressure chemical vapor deposition. A Si0.4Ge0.6 VS with step-graded buffer deposited on Si(001) wafer was used. This VS was post-annealed at 1000°C, followed by chemical-mechanical polishing. After HF dip, the substrate was baked at 850°C in H2, then cooled down to 550°C for epitaxial growth. A 52-82 nm thick Si0.48Ge0.52 layer was deposited using a H2-SiH4-GeH4 gas mixture, then a self-assembled Ge nanodots layer via SK growth mechanism was deposited with 7.5-15.0 nm Ge coverage using a H2-GeH4 gas mixture. This Si0.48Ge0.52/Ge deposition cycle was repeated 5 to 20 times to fabricate the 3D self-ordered Ge nanodot stack. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology and alignment of the Ge nanodots. The facets of the Ge nanodots were studied by analyzing the cross-section cuts of AFM images and confirmed by scanning transmission electron microscopy (STEM). Nano-beam diffraction (NBD) was used to study strain in the superlattice. Fig. 1(a-c) show the AFM images of the 5-cycle superlattices with Ge coverage 7.5 to 15.0 nm. In fig. 1(a), we can see mainly two types of nanodots, diamond (32%) and dome (68%). The height of the diamond-like nanodots is 9 nm with a standard deviation (s) of 2.6 nm while that of the dome-like nanodots is 23 nm with s=1.8 nm. With increasing Ge coverage, dome-like nanodots dominate (fig. 1(b)) and some nanodots merge with the adjacent nanodots (fig. 1(c)). Since the dome-like nanodots show a lower s in height than the diamond-like nanodots do, engineering of self-ordering is more feasible with the dome-like nanodot. Fig. 2(a-b) show the angle view of SEM images of Ge nanodots on 5- and 20-cycle superlattice of 12.5 nm-Ge/52 nm-SiGe. The dome-like nanodots are dominant and laterally aligned. The alignment and the uniformity improve with the increasing cycle number of the superlattice. However, when the thickness of Si0.48Ge0.52 spacer increases, the lateral- and vertical alignment of nanodots become random, and the amount of diamond-like nanodots increases (not shown). To study facets of two types of nanodots, the tilt of each facet was calculated from the cross-section cuts of AFM images. Fig. 3(a) shows an AFM image of the dome-like nanodot. Fig. 3(b) shows the cross-section cuts of fig. 3(a) along . These cross-section cuts are well-overlapped with the high-angle annular dark-field (HAADF) STEM image as shown in the background of fig. 3(b). Therefore, it is possible and reliable to estimate the facets from the cross-section cuts of our AFM images. By this method, we confirmed that the diamond-like nanodot is composed of {105} and the dome-like nanodot is composed of {113} and {159}. This is consistent with a study of Ge dot on Si substrate except for {159} facet (3). Instead of {159} facet, a relatively similar facet {3 15 23} was reported. This difference may result from the less compressive strain in our Ge nanodots because SiGe VS was used. To explain the vertical correlation of Ge nanodots, a HAADF STEM image and in- and out-of-plane strain distributions measured by NBD are shown in fig. 4(a-c). The nanodots are vertically aligned (fig. 4(a)). The SiGe on the nanodot shows a relatively higher lattice parameter along (fig. 4(b)) and lower lattice parameter along (fig. 4(c)) compared to that on Ge wetting layer, indicating tensile strain. This tensile strain area is the preferred position for Ge nanodot formation because of less lateral lattice mismatch. Consequently, the nanodots tend to grow above the buried nanodots. 3D self-ordered multilayered Ge nanodots on SiGe VS were successfully fabricated, and the facets and the vertical correlation of Ge nanodots were studied. References P.S. Chen et al. Materials Science and Engineering B 108 (2004) 213-218 K.L. Wang et al. Proceeding of the IEEE 95 (2007) 1866 J.T. Robinson et al. Nanotechnology 20 (2009) 085708 Figure 1
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- 2022
9. Lateral Selective SiGe Growth for Dislocation-Free Virtual Substrate Fabrication
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Ketan Anand, Markus Andreas Schubert, Agnieszka Anna Corley-Wiciak, Davide Spirito, Cedric Corley-Wiciak, Wolfgang Matthias Klesse, Andreas Mai, Bernd Tillack, and Yuji Yamamoto
- Abstract
Dislocation free local SiGe-on-insulator virtual substrate is fabricated using lateral selective SiGe growth by reduced pressure chemical vapor deposition. The lateral selective SiGe growth is performed around ~1.25 µm square Si (001) pillar in a cavity formed by HCl vapor phase etching of Si at 850 °C from side of SiO2 / Si mesa structure on buried oxide. Smooth root mean square roughness of SiGe surface of 0.14 nm, which is determined by interface roughness between the sacrificially etched Si and the SiO2 cap, is obtained. Uniform Ge content of ~40% in the laterally grown SiGe is observed. In the Si pillar, tensile strain of ~0.65% is found which could be due to thermal expansion difference between SiO2 and Si. In the SiGe, tensile strain of ~1.4% along direction, which is higher compared to that along direction, is observed. The tensile strain is induced from both [110] and [-110] directions. Threading dislocations in the SiGe are located only ~400 nm from Si pillar and stacking faults are running towards directions, resulting in wide dislocation-free area formation in SiGe along due to horizontal aspect ratio trapping.
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- 2022
10. Monolithic and catalyst-free selective epitaxy of InP nanowires on Silicon
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Anagha Kamath, Oliver Skibitzki, Davide Spirito, Shabnam Dadgostar, Irene Mediavilla Martinez, Jorge Serrano, Juan Jimenez, Carsten Richter, Martin Schmidbauer, Albert Kwasniewski, Christian Golz, Markus Andreas Schubert, Gang Niu, and Fariba Hatami
- Abstract
The integration of both optical and electronic components on a single chip, despite the challenge, holds the promise of compatibility with CMOS technology and high scalability. Among all candidate materials, III-V semiconductor nanostructures are key ingredients for opto-electronics and quantum optics devices, such as light emitters and harvesters. The control over geometry, and dimensionality of the nanostructures, enables one to modify the band structures, and hence provide a powerful tool for tailoring the opto-electronic properties of III-V compounds. One of the most creditable approaches towards such growth control is the combination of using patterned wafer and the self-assembled epitaxy. This work presents monolithically integrated catalyst-free InP nanowires grown selectively on nanotip-patterned (001)Si substrates using gas-source molecular-beam epitaxy. The substrates are fabricated using CMOS nanotechnology. The dimensionality of the InP structures can be switched between two-dimensional nanowires and three-dimensional bulk-like InP islands by thermally modifying the shape of Silicon nanotips, surrounded by the SiO2 layer during the oxide-off process. The structural and optical characterization of nanowires indicate the coexistence of both zincblende and wurtzite InP crystal phases in nanowires. The two different crystal structures were aligned with a type-II heterointerface.
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- 2022
11. Three-Dimensional Self-Ordered Multilayered Ge Nanodots on SiGe
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Wei-Chen Wen, Markus Andreas Schubert, Marvin Hartwig Zoellner, Bernd Tillack, and Yuji Yamamoto
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Electronic, Optical and Magnetic Materials - Abstract
Three-dimensional (3D) self-ordered Ge nanodots in cyclic epitaxial growth of Ge/SiGe superlattice on Si0.4Ge0.6 virtual substrate (VS) were fabricated by reduced pressure chemical vapor deposition. The Ge nanodots were formed by Stranski-Krastanov mechanism. By the Ge/SiGe superlattice deposition, dot-on-dot alignment and 〈100〉 alignment were obtained toward the vertical and lateral direction, respectively. Facets and growth mechanism of Ge nanodots and key factors of alignment were studied. Two types of Ge nanodots were observed, diamond-like nanodots composed of {105} and dome-like nanodots composed of {113} and {519} or {15 3 23} facets. The Ge nanodots tend to grow directly above the nanodots of the previous period as these regions show a relatively higher tensile strain induced by the buried nanodots. Thus, this dot-on-dot alignment is sensitive to the SiGe spacer thickness, and it degrades when the SiGe spacer becomes thicker. The Ge content of the SiGe spacer ranging from 45 to 52% affects the lateral alignment and the size uniformity of Ge nanodots because of the strain balance between the superlattice and the VS. By maintaining the strain balance, ordering of the 3D aligned Ge nanodots can be improved.
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- 2023
12. Modulating the Filamentary-Based Resistive Switching Properties of HfO2 Memristive Devices by Adding Al2O3 Layers
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Mai, Mamathamba Kalishettyhalli Mahadevaiah, Eduardo Perez, Marco Lisker, Markus Andreas Schubert, Emilio Perez-Bosch Quesada, Christian Wenger, and Andreas
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bi-layers ,quantum point contact model ,memristive device ,embedded applications ,variability ,conductive filament ,CMOS compatibility - Abstract
The resistive switching properties of HfO2 based 1T-1R memristive devices are electrically modified by adding ultra-thin layers of Al2O3 into the memristive device. Three different types of memristive stacks are fabricated in the 130 nm CMOS technology of IHP. The switching properties of the memristive devices are discussed with respect to forming voltages, low resistance state and high resistance state characteristics and their variabilities. The experimental I–V characteristics of set and reset operations are evaluated by using the quantum point contact model. The properties of the conduction filament in the on and off states of the memristive devices are discussed with respect to the model parameters obtained from the QPC fit.
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- 2022
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13. Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe
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Wei-Chen Wen, Markus Andreas Schubert, Bernd Tillack, and Yuji Yamamoto
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General Engineering ,General Physics and Astronomy - Abstract
Self-ordered multilayered Ge nanodots with SiGe spacers on a Si0.4Ge0.6 virtual substrate are fabricated using reduced-pressure chemical vapor deposition, and the mechanism of vertical ordering is investigated. The process conditions of Ge and SiGe layer deposition are H2-GeH4 at 550 °C and H2-SiH4-GeH4 at 500 °C–550 °C, respectively. By depositing the SiGe at 550 °C or increasing Ge content, the SiGe surface becomes smooth, resulting in vertically aligned Ge nanodots to reduce strain energy. Ge nanodots prefer to grow on the nanodot where the SiGe is relatively tensile strained due to the buried Ge nanodot underneath. By depositing at 500 °C and lowering Ge content, checkerboard-like surface forms, and the following Ge nanodots grow at staggered positions to reduce surface energy. The Ge nanodots are laterally aligned along the elastically soft 〈100〉 direction without pre-structuring resulting from the strain distribution.
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- 2023
14. High Crystallinity Ge Growth on Si (111) and Si (110) by Using Reduced Pressure Chemical Vapor Deposition
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Yuji Yamamoto, Wei-Chen Wen, Markus Andreas Schubert, Cedric Corley-Wiciak, and Bernd Tillack
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Electronic, Optical and Magnetic Materials - Abstract
A method for high quality epitaxial growth of Ge on Si (111) and Si (110) is investigated by reduced pressure chemical vapor deposition. Two step Ge epitaxy (low temperature Ge seed and high temperature main Ge growth) with several cycles of annealing by interrupting the Ge growth (cyclic annealing) is performed. In the case of Ge seed layer growth below 350 °C for (111) and 400 °C for (110) orientation, huge surface roughening due to too high dislocation density is observed after the following annealing step. For both crystal orientations, a high crystallinity Ge seed layer is realized by combination of 450 °C growth with 800 °C annealing. Once the high-quality Ge seed layer is deposited, high crystal quality Ge can be grown at 600 °C on the seed layer for both crystal orientations. For the 5 μm thick Ge layer deposited with the cyclic annealing process at 800 °C, a Si diffusion length of ∼400 nm from the interface, RMS roughness below 0.5 nm and threading dislocation density of 5 × 106 cm−2 are achieved for both (111) and (110) substrates.
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- 2023
15. A 0.13 µm SiGe BiCMOS Technology Featuring fT/fmax of 240/330 GHz and Gate Delays Below 3 ps.
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Holger Rücker, Bernd Heinemann, Wolfgang Winkler, Rainer Barth, Johannes Borngräber, Jürgen Drews, Gerhard G. Fischer, Alexander Fox, Thomas Grabolla, Ulrich Haak, Dieter Knoll, Falk Korndörfer, Andreas Mai, Steffen Marschmeyer, Peter Schley, Detlef Schmidt, J. Schmidt, Markus Andreas Schubert, K. Schulz, Bernd Tillack, Dirk Wolansky, and Yuji Yamamoto
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- 2010
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16. (G03 - Best Student Presentation Award) Lateral Selective SiGe Growth for Dislocation-Free Virtual Substrate Fabrication
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Ketan Anand, Markus Andreas Schubert, Agnieszka Anna Corley-Wiciak, Davide Spirito, Cedric Corley-Wiciak, Wolfgang Matthias Klesse, Andreas Mai, Bernd Tillack, and Yuji Yamamoto
- Abstract
SiGe virtual substrates (VS) having low-surface roughness with less defects are essential for fabricating emerging quantum devices such as qubits. Various techniques to grow VS are reported e.g. conventional graded buffers (1,2) and reverse graded buffers (3). However, these methods require several micrometer-thick buffer layers, having threading dislocations (TDs) network and develop crosshatch patterns resulting in high surface roughness, needing chemical mechanical polishing for planarization. In our previous work, lateral-selective Ge growth (4) was performed in a cavity formed by selective vapor phase etching (VPE) of Si from side of mesa-patterned SiO2 /Si structures fabricated on buried oxide (BOX) to create smooth and dislocation-free local Ge by horizontal aspect ratio trapping (ART). In this work, we demonstrate lateral-selective SiGe growth to realize smooth and dislocation-free local SiGe VS by lateral ART and discuss its surface morphology, strain and dislocations. Lateral-selective SiGe growth is done in a reduced-pressure chemical vapor deposition (RPCVD) system. Thermally oxidized silicon-on-insulator (SOI) wafers with 300 nm SiO2/300 nm Si/2 μm BOX are used. For the sample preparation, 6.3 μm square checkerboard SiO2/Si mesa structure with [110] oriented sidewalls is fabricated by photolithography patterning and reactive ion etching. After standard RCA cleaning followed by HF dip, the wafer is loaded into RPCVD reactor and pre-baked at 850oC in H2 to remove residual oxide. Thereafter, lateral HCl VPE of Si is performed at 850oC from side of mesa. Si pillar remains at center of the mesa. Then, SiGe is selectively deposited in the cavity around the Si pillar using a SiH2Cl2-GeH4-HCl gas mixture at 750oC. Finally, the top SiO2 is removed by HF. Atomic force microscopy (AFM) is used to measure the surface roughness. Energy dispersive X-Ray spectroscopy (EDX) is used for measuring Ge content distribution in SiGe. Micro-Raman spectroscopy is used to analyze strain distribution in Si and SiGe. Nano-beam diffraction (NBD) is employed for estimating the relative change of in- and out-of-plane SiGe lattice parameters. Plan-view transmission electron microscopy (TEM) is used for imaging dislocations. Fig. 1 shows the AFM image for surface morphology of lateral-selective Si0.6Ge0.4 around the Si pillar. SiGe has root mean square roughness of ~0.16 nm, which is similar to blanket Si(001) (~0.14 nm), because the SiGe surface roughness is determined by interface roughness of top SiO2 and sacrificially etched Si. Uniform Ge content of ~40% in SiGe layer is observed by EDX analysis (Fig. 2). In the Si pillar part of Fig. 3, relative uniform tensile-strain of ~0.4% is observed. Since Si is negligibly strained in unpatterned area of SOI (taken as reference), hence during HCl VPE at 850oC, Si pillar/SiO2 interface could slip by higher thermal expansion of Si as interface decreases. Tensile-strain in Si pillar could be formed during cooling process. Ideally, ~1.68% lattice mismatch strain should exist in fully-relaxed ~40% SiGe on Si. However, higher tensile-strain (~2.5%) in SiGe is observed at corners along [010]. To clarify the reason of higher strain at corners, in- and out-of-plane SiGe lattice parameters near Si pillar (as marked in Fig 4(a)) are investigated by NBD. Higher in-plane lattice parameter in [110] is observed in the edge part of the SiGe lamella as compared to the center part (Fig. 4(b)). However, out-of-plane lattice parameter in [001] is homogeneous across entire SiGe (Fig. 4(c)). Because SiGe has uniform Ge concentration as shown in Fig. 2, higher lattice parameter in the edge part of Fig. 4(b) is caused by strain difference. This is because SiGe lamella edge (away from Si pillar) is more relaxed as compared to SiGe lamella center (beside Si pillar) which is confirmed by vertically grown ~700 nm 40% SiGe on blanket Si(110). Symmetric strain distribution does also exist in 90° rotated direction. Therefore, the tensile-strain in [010] is induced from both [110] and [-110]. In Fig. 5, stacking faults of SiGe on (111) plane are observed along [110] and [1-10]. TDs are present along [111], terminated by top SiO2/BOX and located up to first ~400 nm from Si while misfit dislocations are at Si/SiGe interface. Wide dislocation-free area in SiGe is present along [010]. This technique enables dislocation-free local SiGe-on-insulator substrate fabrication which can be applied for thin and high quality VS for the quantum devices. References E. A. Fitzgerald et al., J. Appl. Phys., 63, 693 (1988). E. A. Fitzgerald et al., Appl. Phys. Lett., 59, 811 (1991). V. A. Shah et al., Appl. Phys. Lett., 93, 192103 (2008). Y. Yamamoto et al., ECS J. of Solid State Sci. and Technol., 3, 353 (2014). Figure 1
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- 2022
17. Self-Ordered Ge Nanodot Fabrication by Using Reduced Pressure Chemical Vapor Deposition
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Giovanni Capellini, Yuji Yamamoto, Katsuyoshi Washio, Yuhki Itoh, Peter Zaumseil, Markus Andreas Schubert, Bernd Tillack, Yamamoto, Y., Itoh, Y., Zaumseil, P., Schubert, M. A., Capellini, G., Washio, K., and Tillack, B.
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Fabrication ,Materials science ,business.industry ,Optoelectronics ,Reduced pressure chemical vapor deposition ,Nanodot ,business ,Electronic, Optical and Magnetic Materials - Published
- 2019
18. Strong Electron–Phonon Interaction in 2D Vertical Homovalent III–V Singularities
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Christophe Levallois, Jacky Even, Nicolas Bertru, Antoine Létoublon, Rozenn Piron, Alain Moréac, Olivier Durand, Lipin Chen, Thomas Schroeder, Mathieu Perrin, Rozenn Bernard, Yoan Léger, Charles Cornet, Julie Stervinou, Markus Andreas Schubert, Oliver Skibitzki, Laurent Pedesseau, Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), Innovations for High Performance Microelectronics (IHP), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut für Kristallzüchtung (IKZ) (IKZ), Région Bretagne. China Scholarship Council (CSC) (No. 2017-6254). RENATECH (French Network of Major Technology Centers) within Nanorennes. SIR platform of ScanMAT at University of Rennes 1. HPC resources of TGCC/CINES/IDRIS under the allocation 2019-A0060906724 made by GENCI. Institut Universitaire de France., ANR-14-CE26-0014,ANTIPODE,Analyse approfondie de la nucléation III-V/Si pour les composants photoniques hautement intégrés(2014), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)
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Photoluminescence ,Materials science ,Phonon ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,symbols.namesake ,Condensed Matter::Materials Science ,Ab initio quantum chemistry methods ,0103 physical sciences ,General Materials Science ,010306 general physics ,Condensed matter physics ,business.industry ,General Engineering ,phonon confinement ,Heterojunction ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,electron−phonon interaction ,Semiconductor ,Quantum dot ,2D vertical homovalent singularity ,carrier confinement ,symbols ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Charge carrier ,III−V semiconductor ,0210 nano-technology ,Raman spectroscopy ,business - Abstract
International audience; Highly polar materials are usually preferred over weakly polar ones to study strong electron–phonon interactions and its fascinating properties. Here, we report on the achievement of simultaneous confinement of charge carriers and phonons at the vicinity of a 2D vertical homovalent singularity (antiphase boundary, APB) in an (In,Ga)P/SiGe/Si sample. The impact of the electron–phonon interaction on the photoluminescence processes is then clarified by combining transmission electron microscopy, X-ray diffraction, ab initio calculations, Raman spectroscopy, and photoluminescence experiments. 2D localization and layer group symmetry properties of homovalent electronic states and phonons are studied by first-principles methods, leading to the prediction of a type-II band alignment between the APB and the surrounding semiconductor matrix. A Huang–Rhys factor of 8 is finally experimentally determined for the APB emission line, underlining that a large and unusually strong electron–phonon coupling can be achieved by 2D vertical quantum confinement in an undoped III–V semiconductor. This work extends the concept of an electron–phonon interaction to 2D vertically buried III–V homovalent nano-objects and therefore provides different approaches for material designs, vertical carrier transport, heterostructure design on silicon, and device applications with weakly polar semiconductors.
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- 2020
19. Ge/SiGe multiple quantum well fabrication by reduced-pressure chemical vapor deposition
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Mario Scuderi, Yuji Yamamoto, Oliver Skibitzki, Marvin Zöllner, Monica De Seta, Giovanni Capellini, Felix Reichmann, Markus Andreas Schubert, Bernd Tillack, Yamamoto, Y., Skibitzki, O., Schubert, M. A., Scuderi, M., Reichmann, F., Zollner, M. H., De Seta, M., Capellini, G., and Tillack, B.
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010302 applied physics ,Materials science ,Fabrication ,Physics and Astronomy (miscellaneous) ,business.industry ,General Engineering ,General Physics and Astronomy ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Strain energy ,Stack (abstract data type) ,0103 physical sciences ,Optoelectronics ,Growth rate ,Dislocation ,0210 nano-technology ,business ,Layer (electronics) - Abstract
In this paper we have deposited structures comprising a stack of 10 periods made of 15 nmthick Ge multi quantum well (MQW) enclosed in 15 nm-thick Si0.2Ge0.8 barrier have been deposited on SiGe virtual substrates (VS) featuring different Ge contents in the 85% - 100% Ge range to investigate the influence of heteroepitaxial strain on the Si0.2Ge0.8 and Ge growth. With increasing Ge concentration of the VS, growth rate of the Si0.2Ge0.8 in the MQW increases. Si incorporation into the Si0.2Ge0.8 layer becomes also slightly higher. However, almost no influence of the growth rate is observed for Ge growth in the MQW. We argue that the increased tensile strain promotes the Si reaction at the surface. In the case of the Si0.2Ge0.8 growth on Ge, we observe a smeared interface due to the Ge segregation during the growth. Furthermore, we observe that this interface width increases with increasing Ge concentration of VS. We attribute this observation to the increased segregation of Ge driven by the increased strain energy accumulated in the in the Si0.2Ge0.8 layers. We also observed that the MQW layer “filters-out” threading dislocations formed in the VS.
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- 2020
20. Self-Ordered Ge Nanodot Fabrication by Reduced Pressure Chemical Vapor Deposition
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Yuji Yamamoto, Giovanni Capellini, Peter Zaumseil, Katsuyoshi Washio, Bernd Tillack, Yuhki Itoh, and Markus Andreas Schubert
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Fabrication ,Materials science ,Chemical engineering ,Reduced pressure chemical vapor deposition ,Nanodot - Published
- 2018
21. Current Stage of the Investigation of the Composition of Oxygen Precipitates in Czochralski Silicon Wafers
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Andreas Sattler, Markus Andreas Schubert, Dawid Kot, and G. Kissinger
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010302 applied physics ,Materials science ,Metallurgy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Oxygen precipitates ,0103 physical sciences ,Wafer ,Composition (visual arts) ,Stage (hydrology) ,Current (fluid) ,0210 nano-technology - Published
- 2017
22. Abrupt SiGe and Si Profile Fabrication by Introducing Carbon Delta Layer
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Junichi Murota, Markus Andreas Schubert, Anne Hesse, Peter Zaumseil, Yuji Yamamoto, and Bernd Tillack
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010302 applied physics ,Delta ,Materials science ,Fabrication ,business.industry ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Layer (electronics) ,Carbon - Published
- 2017
23. Investigation of stoichiometry of oxygen precipitates in Czochralski silicon wafers by means of EDX, EELS and FTIR spectroscopy
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A. Sattler, Markus Andreas Schubert, G. Kissinger, M. Klingsporn, A. Huber, and D. Kot
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010302 applied physics ,Materials science ,Silicon ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Amorphous solid ,chemistry ,Absorption band ,0103 physical sciences ,General Materials Science ,Wafer ,Electrical and Electronic Engineering ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Spectroscopy ,Stoichiometry - Abstract
In this work, we used EDX, EELS and FTIR spectroscopy to investigate the stoichiometry of oxygen precipitates in Czochralski silicon wafers. The EDX analysis of a plate-like precipitate demonstrated that the composition of the precipitate is SiO1.93. This result was confirmed by EELS where the characteristic plasmon peak of SiO2 was observed. Additionally, the absorption band of plate-like precipitates at 1223 cm−1 was found in the FTIR spectrum measured at liquid helium temperature. It was demonstrated that this band can only be simulated by the dielectric constants of amorphous SiO2.
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- 2016
24. Advanced Coherent X-ray Diffraction and Electron Microscopy of Individual InP Nanocrystals on Si Nanotips for III-V-on- Si Electronics and Optoelectronics
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Steven J. Leake, Peter Zaumseil, Zuo-Guang Ye, Marie-Ingrid Richard, Felix Kießling, Thomas Schroeder, Tobias U. Schülli, Tore Niermann, William Ted Masselink, Giovanni Capellini, Markus Andreas Schubert, Fariba Hatami, Michael Lehmann, Gang Niu, Jerome Carnis, Wei Ren, Oliver Skibitzki, and Emad H. Hussein
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Nanostructure ,Materials science ,Condensed matter physics ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Imaging phantom ,law.invention ,Crystal ,Nanocrystal ,law ,0103 physical sciences ,X-ray crystallography ,Electron microscope ,010306 general physics ,0210 nano-technology - Abstract
Let's talk about your flaws\dots{} The authors present nondestructive examination of the crystallographic properties (including crystal size, facet shape, strain, and defects) of lone InP nanocrystals (NC) grown on Si nanostructures. This sort of three-dimensional structured imaging is of great significance in evaluating the quality of the active nanomaterials in fully processed nanoelectronic and nano-optoelectronic devices, even in an $o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}o$ manner.
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- 2019
25. Operando diagnostic detection of interfacial oxygen ‘breathing’ of resistive random access memory by bulk-sensitive hard X-ray photoelectron spectroscopy
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Peng Huang, Thomas Schroeder, Markus Andreas Schubert, Christian Wenger, Jinfeng Kang, Florian Bärwolf, Stefan Petzold, Andrei Gloskovskii, Lambert Alff, Yudi Zhao, S. U. Sharath, Wei Ren, P. Calka, Zuo-Guang Ye, Karol Fröhlich, Gang Niu, and Eduardo Perez
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,RRAM ,01 natural sciences ,Oxygen ,X-ray photoelectron spectroscopy ,ddc:670 ,Oxygen breathing ,0103 physical sciences ,lcsh:TA401-492 ,HAXPES ,General Materials Science ,HfO2 ,010302 applied physics ,Hardware_MEMORYSTRUCTURES ,resistive switching ,business.industry ,021001 nanoscience & nanotechnology ,Resistive random-access memory ,chemistry ,Resistive switching ,interface ,Optoelectronics ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology ,business - Abstract
Materials Research Letters 7(3), 117 - 123 (2019). doi:10.1080/21663831.2018.1561535, The HfO2-based resistive random access memory (RRAM) is one of the most promising candidatesfor non-volatile memory applications. The detection and examination of the dynamic behavior ofoxygen ions/vacancies are crucial to deeply understand the microscopic physical nature of theresistive switching (RS) behavior. By using synchrotron radiation based, non-destructive and bulksensitivehard X-ray photoelectron spectroscopy (HAXPES), we demonstrate an operando diagnosticdetection of the oxygen ‘breathing’ behavior at the oxide/metal interface, namely, oxygen migrationbetween HfO2 and TiN during different RS periods. The results highlight the significance ofoxide/metal interfaces in RRAM, even in filament-type devices., Published by Taylor & Francis, London [u.a.]
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- 2019
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26. Shallow and undoped germanium quantum wells: a playground for spin and hybrid quantum technology
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Amir Sammak, Diego Sabbagh, Nico W. Hendrickx, Mario Lodari, Brian Paquelet Wuetz, Alberto Tosato, LaReine Yeoh, Monica Bollani, Michele Virgilio, Markus Andreas Schubert, Peter Zaumseil, Giovanni Capellini, Menno Veldhorst, Giordano Scappucci, Sammak, Amir, Sabbagh, Diego, Hendrickx, Nico W., Lodari, Mario, Paquelet Wuetz, Brian, Tosato, Alberto, Yeoh, Lareine, Bollani, Monica, Virgilio, Michele, Schubert, Markus Andrea, Zaumseil, Peter, Capellini, Giovanni, Veldhorst, Menno, and Scappucci, Giordano
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quantum well ,chemistry.chemical_element ,Germanium ,High Tech Systems & Materials ,02 engineering and technology ,spin ,010402 general chemistry ,01 natural sciences ,Biomaterials ,Condensed Matter::Materials Science ,Effective mass (solid-state physics) ,Electrochemistry ,germanium QW ,Quantum well ,Surface states ,Physics ,Industrial Innovation ,Condensed matter physics ,business.industry ,Heterojunction ,quantum technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,mobility ,germanium ,quantum devices ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Quantum technology ,Semiconductor ,chemistry ,Field-effect transistor ,0210 nano-technology ,business - Abstract
Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 105 cm2 V−1 s−1) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 1011cm−2, light effective mass (0.09me), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.
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- 2019
27. Threading Dislocation Reduction of Ge by Introducing a SiGe/Ge Superlattice
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Yuji Yamamoto, Bernd Tillack, Marvin Zöllner, Cedric Corley, and Markus Andreas Schubert
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Materials science ,Annealing (metallurgy) ,business.industry ,Superlattice ,medicine.medical_treatment ,Pit formation ,Electronic, Optical and Magnetic Materials ,Si substrate ,Surface roughening ,Lattice (order) ,Surface roughness ,medicine ,Threading (manufacturing) ,Optoelectronics ,Dislocation ,business ,Reduction (orthopedic surgery) - Abstract
The influence of introducing a SiGe/Ge superlattice (SL) between Ge layers and Si substrate for the sake of the reduction of the threading dislocation density (TDD) without additional annealing is investigated. By introducing the SiGe/Ge SL and optimizing the layer stack, the TDD of the Ge layer becomes ∼1/3. In the case of 2.8 μm thick Ge without introducing the SiGe/Ge SL, the TDD at the surface is 7.6 × 108 cm−2. A slight TDD reduction is observed by introducing a Si0.2Ge0.8/Ge SL between the Si substrate and the Ge layer. By inserting 5, 10 and 20 cycles of Si0.2Ge0.8/Ge, the TDD is reduced to 7.1 × 108, 5.9 × 108 and 5.3 × 108 cm−2, respectively. The lateral lattice parameters of these SLs are ∼5.656 Å, which is a smaller value compared to that of bulk Ge, indicating plastic relaxation by misfit dislocation formation. Further TDD reduction is realized with increasing Si concentration in the SiGe/Ge SL without changing the cycle of the SL. However, surface roughening due to pit formation occurs if the Si concentration in the SL is higher than 50% because of increased strain at the interfaces between SiGe and Ge. With increasing SiGe and Ge thickness ratio in the SL layer and maintaining periodicity and cycles, the TDD is reduced to 2.8 × 108 cm−2 without degrading the surface roughness. This improvement is related to a relaxation of the SiGe/Ge SL by plastic deformation.
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- 2021
28. Threading Dislocation Reduction of Ge by Introducing a SiGe/Ge Superlattice
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Yuji Yamamoto, Cedric Corley, Markus Andreas Schubert, Marvin Zöllner, and Bernd Tillack
- Abstract
Ge growth on Si is essential e.g. for photonics device integration (e.g. Ge photodiode) into Si based CMOS platform (1). However, due to 4.2% of lattice mismatch between Ge and Si, misfit dislocations (MD) and threading dislocations (TD) are introduced for strain relaxation after exceeding critical thickness. In order to realize low-darkcurrent Ge photodiode, improvement of crystallinity is important. High quality Ge growth techniques by combining various annealing techniques (at 800~850oC) are reported (2-3). However, because of low melting point of Ge (937oC), the Ge growth process is typically integrated at the last part of front-end process. Therefore, these annealing processes are affecting device parameters of existing devices. In previous paper, we reported Ge/SiGe superlattice (SL) fabrication and found improvement of TD density (TDD) by increasing Si composition of SiGe in the SL (4). Here we report TDD improvement of Ge by introducing the SL without annealing. Ge growth with SiGe/Ge SL is carried out using reduced pressure chemical vapor deposition system. Si(100) wafers are used. After an HF last cleaning, the wafer is loaded into reactor and baked at 1000oC and cooled down to 600oC in H2 and further cooled down to 350oC in N2. After that 100 nm-thick seed Ge is deposited using N2-GeH4 gas. Then the wafer is heated up to 500oC in H2 and Ge/SiGe superlattice is fabricated using H2-GeH4 and H2-SiH4-GeH4 gases, respectively. Furthermore, 2.8 µm thick Ge is deposited at 550oC using H2-GeH4 gas. Thickness is measured by cross section SEM and spectroscopic ellipsometry. TDD is determined by Secco defect etching technique. Strain and relaxation of Ge and SiGe layers are measured by XRD reciprocal space mapping. Distribution of the MD and the TD are measured by cross section TEM. In the case of direct Ge growth on Si (Fig. 1a), MDs are formed at interface between Ge and Si. TDs are spreading into the Ge layer. Some of the TDs are long and extending to surface. These MD and TD formations are due to the lattice mismatch between Ge and Si. On the other hand, in the case of Ge sample grown on ×20 Si0.3Ge0.7 / Ge SL (Fig. 1b), most of MDs are formed at interface between 100 nm-thick Ge buffer and Si substrate. Additionally high density of TDs are observed in the Ge buffer and the SL layer. In the SL layer, lower TDD is observed in the upper part compared to that in the deeper part. At the interface between upper 2.8 µm thick Ge and the SL layer, MD and high density of TDs toward lateral direction is observed indicating relaxation. TDD in the 2.8 µm thick Ge layer seems to be lower compared to that in Fig. 1a). In the case of direct Ge growth on Si, TDD of ~7.5×108 cm-2 is obtained (Fig. 2). The TDD is comparable to previously reported results (2). By depositing 2.8 µm thick Ge on Si0.2Ge0.8 SL, TDD is decreased to ~5.4×108 cm-2. With decreasing Ge concentration of SiGe layer of the SL, decrease of TDD is observed until 40%. However, by replacing SiGe layers to mono-layers of Si, increased TDD is observed, which might be due to too high strain at interface between Si and SiGe. Figure 3 shows TDD of 2.8 µm thick Ge deposited on Si0.2Ge0.8/Ge SL with different Si0.2Ge0.8 and Ge thickness combination without changing periodicity of the SL. Lower TDD is observed when the 2.8 µm thick Ge is deposited on the SL with higher Si0.2Ge0.8 thickness. Possible reason is higher degree of relaxation of the SL layer. In Fig. 4, TDD of 2.8 µm thick Ge deposited on SLs of various lattice parameters are shown. By reducing lateral lattice parameter of the SiGe/Ge SL by increasing SiGe thickness or Si concentration, TDD decreases. The reduction of the TDD is fitting to one line for both cases. These results indicate that higher plastic relaxation of the SL occurs on the Ge buffer due to increased compressive strain of SiGe in the SL, and the TDD reduction of the Ge on the SL may be caused by similar mechanism of reverse graded buffer. By introducing SiGe/Ge SL, multiple effect of the reverse graded buffer may be expected. Reference (1) S. Lischke et al. Proc. IEEE Bipolar/BiCMOS Circuits and Technology Meeting (BCTM) , (2014) 29 (2) Y. Yamamoto et al Solid-State Electron. 60 (2011) 2 (3) Y. Yamamoto et al. Semicond. Sci. Technol. 33 (2018) 124007 (4) Y. Yamamoto et al. Jpn. J. Appl. Phys. 59, SGGK10 (2020) Figure 1
- Published
- 2020
29. (Invited) Current Stage of the Investigation of the Composition of Oxygen Precipitates in Czochralski Silicon Wafers
- Author
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Markus Andreas Schubert, Andreas Sattler, Dawid Kot, and Gudrun Kissinger
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Crystallography ,Materials science ,Oxygen precipitates ,Metallurgy ,Wafer ,Stage (hydrology) ,Current (fluid) - Abstract
The oxygen precipitates formed in Czochralski (CZ) silicon wafers in consequence of the thermal treatment were investigated since many decades. The main reason why so much effort was directed towards these defects was the impact which they have on integrated circuits and properties of silicon wafer itself. Oxygen precipitates can increase the resistivity of CZ silicon, change the wafer strength and cause warpage of the wafers. It was also demonstrated that metal impurities can be effectively trapped at oxygen precipitates in the process of gettering, what is a huge advantage. All these features of the oxygen precipitates require the control of precipitation in the production process of silicon devices. However, this cannot be optimally executed if the features of oxygen precipitates like their composition are not fully known. In spite of the wide knowledge of oxygen precipitation, the composition of oxygen precipitates SiO x still remains under ongoing discussion. This is due to the different x values varying from x=1 to x=2 which can be found in the literature. In this work, we look on the current stage of the investigation on the composition of oxygen precipitates obtained with the help of different techniques. Moreover, we present our recent investigation on the composition of oxygen precipitates carried out by means of energy dispersive X-ray spectroscopy (EDX), electron energy loss spectroscopy (EELS) and Fourier transform infrared spectroscopy (FTIR). The FTIR spectra measured at liquid helium temperature will be compared with the spectra simulated on the basis of experimental results obtained by scanning transmission electron microscopy (STEM). The EDX gives direct information about the composition of oxygen precipitates. However, the analysis of the EDX spectrum requires a special calibration. This is due to the limitation of EDX for light elements like oxygen. The intensity of characteristic X-rays of oxygen depends on the thickness of TEM lamellae. Therefore, in this work we measured a thermally grown SiO2 layer at different thickness of TEM lamellae in order to determine the influence of the lamellae thickness on the intensity of oxygen characteristic X-rays. After doing this, we measured the composition of oxygen precipitates located at very thin TEM lamellae. The results shown that x is in the range between 1.8 and 1.9 (1). To make sure that the EDX results are correct EELS measurements were carried out. EELS is a complementary method to EDX. It allows to avoid the limitation of EDX in the measurement of the composition of oxygen precipitate especially in the case if the precipitate does not go through the TEM lamellae. Deconvoluting the characteristic plasmons of Si, SiO2 and suboxides in the electron energy loss spectra we found that the oxygen precipitate consist of SiO2 and it is coated by thin 2-3nm SiO layer (2). Finally, we investigated the composition of oxygen precipitates by FTIR. The absorption band of oxygen precipitates were observed in FTIR spectra measured at liquid helium temperature. The position and the shape of the bands fit very well to the simulated spectra. The simulation of the spectra was conducted on the basis of the effective medium theory (EMT) where we considered SiO2 spheroids coated by SiO layers embedded in a Si matrix. In summary, the composition of oxygen precipitates was investigated by EDX, EELS and FTIR whereby the first two methods are direct methods and the latter one is an indirect method. All methods delivered similar results. Hence, we can conclude that the oxygen precipitates consist of a SiO2 core which is coated by an SiO layer. References 1D. Kot, G. Kissinger, M. A. Schubert, M. Klingsporn, A. Huber, and A. Sattler, Phys. Status Solidi RRL 9, 405 (2015). 2G. Kissinger, D. Kot, M. Klingsporn, M.A. Schubert, A. Sattler, T. Müller, ECS J. Solid State Sci. Technol. 4 (9), N124-N129 (2015).
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- 2016
30. Investigation of the Composition of the Si/SiO2 Interface in Oxide Precipitates and Oxide Layers on Silicon by STEM/EELS
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Markus Andreas Schubert, Thomas Grabolla, Gudrun Kissinger, and Dawid Kot
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010302 applied physics ,Materials science ,Silicon ,Inorganic chemistry ,Metallurgy ,Analytical chemistry ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Octahedron ,Ionization ,0103 physical sciences ,0210 nano-technology ,Layer (electronics) ,Stoichiometry ,Plasmon - Abstract
In a previous work, we found that both the interface between an oxide precipitate and the surrounding silicon matrix and the interface between a silicon substrate and a thermal oxide layer are of the same nature [1]. In both cases, between SiO2 existing in the center of the precipitate and in the oxide layer and Si of the matrix and the substrate a suboxide region of 2-3 nm exists. These results were obtained by electron energy loss spectrometry (EELS) carried out by scanning transmission electron microscopy (STEM). In the low loss region, it is possible to distinguish between Si, SiO, and SiO2 which all exhibit different maxima of the plasmon loss energy. By deconvolution, the local composition of the phase can be determined with the help of reference spectra of the three components. The stoichiometry of the oxide precipitates (SiO x ) was debated for a long time and application of different methods on different samples containing oxygen precipitates resulted in different values for x ranging from 1 to 2. Recently, it was demonstrated by applying several direct and indirect methods that the oxide precipitates consist of SiO2 [2]. Inspired by the results in Ref. 1 and 2, a layer model was proposed explaining the different values for x for oxide precipitates of different geometry [3]. Especially, for plate-like precipitates with a large surface the lower x values could be explained. Now the question came up if the width of the interface between Si and SiO2 is constant for all growth temperatures because from interface physics it could be expected that its width increases with temperature. Another point is, if the thickness of oxide layer or oxide precipitates plays a role. For this reason, we again used thermal oxide layers on (100) silicon of different thickness grown at different temperature to investigate the composition profile across the interface. We also compared the results with profiles from plate-like oxide precipitates grown at different temperatures. A scanning transmission electron microscope (STEM) FEI Tecnai Osiris equipped with tools for energy dispersive X-ray spectroscopy (EDX) analysis and EELS was used to analyze the interface and composition of a plate-like precipitates located at a very thin place of the lamella prepared from the sample by grinding, polishing, and ion milling. The profiles of the x values across the interfaces of the oxide layers and the precipitates were determined from the deconvolution of the Si, SiO, and SiO2 EELS spectra. The results of these investigations demonstrate that the stoichiometry of SiO2 (x=2) cannot be reached if the oxide layer thickness is lower than 10 nm for thermal oxides grown at 900 °C. The lower the thickness of the layer is the lower is the maximum x value. This is due to an interface layer of equal maximum slope for all oxide layers. The slope was obtained from fitting by sigmoid functions. Such interface layers were also found for the oxide precipitates but the maximum slope is lower. It was found to increase with increasing diffusion length of interstitial oxygen. The maximum of the x profiles also depends on the thickness of the plate-like oxide precipitates. The results will be discussed with respect to the phase separation process leading to precipitation of interstitial oxygen in silicon. References [1] G. Kissinger, D. Kot, M. Klingsporn, M.A. Schubert, A. Sattler, T. Müller, ECS J. Solid State Sci. Technol. 4 (9), N124-N129 (2015). [2] D. Kot, G. Kissinger, M. A. Schubert, M. Klingsporn, A. Huber, and A. Sattler, Phys. Status Solidi RRL 9, 405 (2015). [3] J. Vanhellemont, Phys. Status Solidi RRL 9, 597 (2015).
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- 2016
31. Photoluminescence from GeSn nano-heterostructures
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Monica De Seta, Peter Zaumseil, Markus Andreas Schubert, Wolfgang M. Klesse, Thomas Schroeder, Michele Virgilio, Viktoria Schlykow, Yaonan Hou, Oliver Skibitzki, Luciana Di Gaspare, Yuji Yamamoto, Giovanni Capellini, Schlykow, Viktoria, Zaumseil, Peter, Schubert, Markus Andrea, Skibitzki, Oliver, Yamamoto, Yuji, Klesse, Wolfgang Matthia, Hou, Yaonan, Virgilio, Michele, De Seta, Monica, Di Gaspare, Luciana, Schroeder, Thoma, and Capellini, Giovanni
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GeSn ,nanoheteroepitaxy ,photoluminescence ,Bioengineering ,Chemistry (all) ,Materials Science (all) ,Mechanics of Materials ,Mechanical Engineering ,Electrical and Electronic Engineering ,Photoluminescence ,Materials science ,Analytical chemistry ,02 engineering and technology ,01 natural sciences ,0103 physical sciences ,General Materials Science ,Deposition (law) ,Wetting layer ,Eutectic system ,010302 applied physics ,technology, industry, and agriculture ,Heterojunction ,General Chemistry ,021001 nanoscience & nanotechnology ,Wetting ,0210 nano-technology ,Layer (electronics) ,Molecular beam epitaxy - Abstract
We investigate the distribution of Sn in GeSn nano-heteroepitaxial clusters deposited at temperatures well exceeding the eutectic temperature of the GeSn system. The 600 °C molecular beam epitaxy on Si-patterned substrates results in the selective growth of GeSn nano-clusters having a 1.4 ± 0.5 at% Sn content. These nano-clusters feature Sn droplets on their faceted surfaces. The subsequent deposition of a thin Ge cap layer induced the incorporation of the Sn atoms segregated on the surface in a thin layer wetting the nano-dots surface with 8 ± 0.5 at% Sn. The presence of this wetting layer is associated with a relatively strong photoluminescence emission that we attribute to the direct recombination occurring in the GeSn nano-dots outer region.
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- 2018
32. Alignment control of self-ordered three dimensional SiGe nanodots
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Francesco Montalenti, Yuhki Itoh, Yuji Yamamoto, Katsuyoshi Washio, Giovanni Capellini, Peter Zaumseil, Markus Andreas Schubert, Bernd Tillack, Yamamoto, Y., Itoh, Y., Zaumseil, P., Schubert, M. A., Capellini, G., Montalenti, F, Washio, K., Tillack, B., Yamamoto, Y, Itoh, Y, Zaumseil, P, Schubert, M, Capellini, G, Washio, K, and Tillack, B
- Subjects
Materials Chemistry2506 Metals and Alloys ,Diffraction ,Materials science ,SiGe ,Condensed Matter Physic ,02 engineering and technology ,Chemical vapor deposition ,01 natural sciences ,chemical vapor deposition ,Tetragonal crystal system ,strain ,Chemical-mechanical planarization ,0103 physical sciences ,Nano ,Materials Chemistry ,Electrical and Electronic Engineering ,FIS/03 - FISICA DELLA MATERIA ,Deposition (law) ,010302 applied physics ,business.industry ,Electronic, Optical and Magnetic Material ,nanodot ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Surface energy ,Electronic, Optical and Magnetic Materials ,surface energy ,Optoelectronics ,Nanodot ,0210 nano-technology ,business - Abstract
Alignment control of three dimensional (3D) SiGe nanodot arrangements is investigated using a reduced pressure chemical vapor deposition system. Several cycles of SiGe layers with 30% Ge content and Si spacers are deposited by SiH4-GeH4 at 550 °C and SiH4 or SiH2Cl2 at 700 °C, respectively, to form a 3D SiGe nanodot structure. By using SiH4 as a precursor for the Si spacer deposition, SiGe nanodots are aligned at staggered positions resulting in a body-centered tetragonal (BCT) structure, because a checkerboard mesa structured Si surface is formed and the next SiGe nanodot formation occurs at the concave region to reduce surface energy. On the other hand, after planarizing the Si surface with checkerboard structure by chemical mechanical polishing (CMP), the new SiGe nanodot formation occurs directly above the embedded SiGe nanodot located nearest to the Si surface (dot-on-dot). The driving force seems to be local tensile strain formed at the Si surface above the embedded SiGe nanodot. By using SiH2Cl2 as precursor for the Si spacer deposition, a smooth Si surface can be realized on BCT SiGe nanodot structures without CMP process resulting in a vertically aligned SiGe nanodot formation. The local tensile strain formation in Si above SiGe nanodots is confirmed by nano beam diffraction analysis.
- Published
- 2018
33. Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back
- Author
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Peter Zaumseil, Francesco Montalenti, Markus Andreas Schubert, G Schwalb, Anna Marzegalli, F Rovaris, Monica De Seta, Thomas Schroeder, Giovanni Capellini, Carsten Richter, Luciana Di Gaspare, Tobias U. Schülli, Peter Storck, Marvin Hartwig Zoellner, Rovaris, F, Zoellner, M, Zaumseil, P, Schubert, M, Marzegalli, A, Di Gaspare, L, De Seta, M, Schroeder, T, Storck, P, Schwalb, G, Richter, C, Schülli, T, Capellini, G, Montalenti, F, Rovaris, Fabrizio, Zoellner, Marvin H., Zaumseil, Peter, Schubert, Markus A., Marzegalli, Anna, Di Gaspare, Luciana, De Seta, Monica, Schroeder, Thoma, Storck, Peter, Schwalb, Georg, Richter, Carsten, Schülli, Tobias U., Capellini, Giovanni, and Montalenti, Francesco
- Subjects
Materials science ,Condensed matter physics ,Heteroepitaxy, modeling, cross-hatch ,Mesoscale meteorology ,General Physics and Astronomy ,Heterojunction ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Characterization (materials science) ,Crystal ,Condensed Matter::Materials Science ,Tilt (optics) ,Lattice (order) ,0103 physical sciences ,Relaxation (physics) ,Dislocation ,010306 general physics ,0210 nano-technology - Abstract
We provide an in-depth characterization of the dislocation distribution in partially relaxed Si0.92Ge0.08/Si(001) films. This is achieved by an innovative and general method, combining two state-of-the-art characterization techniques through suitable modeling. After having inferred the dislocation positions from transmission-electron-microscopy images, we theoretically reproduce scanning-x-ray-diffraction-microscopy tilt maps measured on the very same region of the sample. We obtain a nearly perfect match between model predictions and experimental data. As a result, we claim that it is possible to establish a local, direct correlation between the dislocations revealed by the transmission-electron-microscopy analysis and the measured lattice tilt distribution.
- Published
- 2018
34. Internal Gettering of Copper for Microelectronic Applications
- Author
-
Markus Andreas Schubert, Dawid Kot, Timo Müller, Andreas Sattler, and Gudrun Kissinger
- Subjects
Materials science ,Silicon ,business.industry ,Metallurgy ,chemistry.chemical_element ,Contamination ,Condensed Matter Physics ,Copper ,Atomic and Molecular Physics, and Optics ,chemistry ,Oxygen precipitates ,Getter ,Impurity ,Microelectronics ,General Materials Science ,Wafer ,business - Abstract
The results of this work have shown that for microelectronic applications, gettering at dislocations is less important and oxygen precipitates are the main getter sink for Cu. Sufficient gettering of Cu in samples contaminated with low Cu concentration requires a higher density and larger oxygen precipitates compared to samples contaminated with high Cu concentration. It is demonstrated that the getter efficiency depends on the contamination level of the samples and getter test with low contamination level must be applied for microelectronic applications. Furthermore, a getter test for 3D chip stack technologies was developed. It was shown that although the wafers are thinned to a thickness of 50 μm their getter efficiency seems to be higher than for wafers of the original thickness. This is assumed to be due to the higher Cu concentration in the thinner wafers which can be gettered easier. It is also demonstrated that BMDs can getter Cu impurities even if the temperature does not exceed 300 °C. The getter efficiency tends to be higher if the samples are stored under day light and not in the dark.
- Published
- 2015
35. Lateral solid phase epitaxy of amorphously grown Si1−xGex layers on SiO2/Si(100) substrates using in-situ RPCVD postannealing
- Author
-
Yuji Yamamoto, Oliver Skibitzki, Bernd Tillack, and Markus Andreas Schubert
- Subjects
Materials science ,business.industry ,Annealing (metallurgy) ,Heterojunction bipolar transistor ,Metals and Alloys ,Nucleation ,Surfaces and Interfaces ,Epitaxy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Monocrystalline silicon ,Electrical resistivity and conductivity ,Materials Chemistry ,Optoelectronics ,Wafer ,business - Abstract
Lateral solid phase epitaxy (L-SPE) in non-doped or in-situ B-doped amorphous- (a-) SiGe deposited on SiO 2 patterned Si(100) wafers by in-situ postannealing in reduced pressure chemical vapor deposition system was investigated for possible heterojunction bipolar transistor (HBT) base link resistivity improvement. Using Si 2 H 6 as Si precursor gas, an epitaxial and amorphous layer was grown on the mask window and on the SiO 2 area, respectively. By inserting a-Si buffer underneath, the deposited a-SiGe surface became smoother. After the L-SPE process, an improved L-SPE length was observed due to suppressed random nucleation on SiO 2 . The L-SPE length increased with increasing postannealing time and saturated due to random poly-grain formation on the SiO 2 . At the same L-SPE time, increased L-SPE length was observed at higher temperature and at higher Ge concentration. With increasing B concentration in the a-SiGe, the L-SPE length firstly increased. However, after reaching 2 × 10 19 atom/cm 3 , the L-SPE length reduced again down to the undoped case. These results of L-SPE process might have potential to improve dynamic performance of SiGe HBT by reducing the base link resistivity by widening the monocrystalline region around bipolar window.
- Published
- 2015
36. Composition of oxygen precipitates in Czochralski silicon wafers investigated by STEM with EDX/EELS and FTIR spectroscopy
- Author
-
Gudrun Kissinger, Andreas Sattler, Andreas Huber, Dawid Kot, Max Klingsporn, and Markus Andreas Schubert
- Subjects
Materials science ,Silicon ,Electron energy loss spectroscopy ,Analytical chemistry ,chemistry.chemical_element ,Dielectric ,Condensed Matter Physics ,Amorphous solid ,chemistry ,Absorption band ,General Materials Science ,Wafer ,Fourier transform infrared spectroscopy ,Stoichiometry - Abstract
In this work, we investigated the stoichiometry of oxygen precipitates in Czochralski silicon wafers. The thickness dependence of the Cliff–Lorimer sensitivity factor for the silicon/oxygen system was determined and applied for the investigation of the stoichiometry of oxygen precipitates by EDX. The results show that both plate-like oxygen precipitates and a transitional form between plate-like and octahedral precipi- tates consist of SiO2. This was confirmed by EELS low loss spectra where the typical spectrum for amorphous SiO2 was observed. Moreover, the absorption band of plate-like precipitates at 1227 cm–1 was found in the low temperature FTIR spectrum. It was demonstrated that this band can only be simulated by the dielectric constants of amorphous SiO2. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)
- Published
- 2015
37. AlN/SiO2/Si3N4/Si(100)-Based CMOS Compatible Surface Acoustic Wave Filter With −12.8-dB Minimum Insertion Loss
- Author
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Mirko Fraschke, Dirk Wolansky, Thomas Schroeder, Christian Wipf, Christian Wenger, Udo Christian Kaletta, and Markus Andreas Schubert
- Subjects
Diffraction ,Materials science ,business.industry ,Surface acoustic wave ,Analytical chemistry ,Particle displacement ,Nitride ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Transducer ,CMOS ,symbols ,Optoelectronics ,Insertion loss ,Electrical and Electronic Engineering ,Rayleigh scattering ,business - Abstract
A CMOS compatible AlN/SiO2/Si3N4/Si(100) surface acoustic wave (SAW) device has been fabricated and will be compared with standard AlN/SiO2-based devices. The presented filter demonstrates high potential for CMOS integrated high-frequency SAW devices. The filter insertion loss could be improved to −12.8 dB. The device exhibits high crosstalk suppression of −50 dB on a standard Si-substrate (10 $\Omega $ cm). X-ray diffraction, (scanning) transmission electron microscopy, and energy dispersive X-ray spectroscopy studies correlate the signal quality with $c$ -axis orientation of aluminum nitride films on interdigitated transducer finger electrodes. Finite-element method simulations are in good agreement with the electric measurements and show typical Rayleigh particle displacement.
- Published
- 2015
38. Investigation of the Copper Gettering Mechanism of Oxide Precipitates in Silicon
- Author
-
M. Klingsporn, Markus Andreas Schubert, Dawid Kot, G. Kissinger, Timo Müller, and Andreas Sattler
- Subjects
Interface layer ,Materials science ,Silicon ,Metallurgy ,Oxide ,chemistry.chemical_element ,Silicon matrix ,Copper ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Thermal oxide ,Getter ,Layer (electronics) - Abstract
One of the reasons why the principal gettering mechanism of copper at oxide precipitates is not yet clarified is that it was not possible to identify the presence and measure the copper concentration in the vicinity of oxide precipitates. To overcome the problem we used a 14.5 nm thick thermal oxide layer as a model system for an oxide precipitate to localize the place where the copper is collected. We also analyzed a plate-like oxide precipitate by EDX and EELS and compared the results with the analysis carried out on the oxide layer. It is demonstrated that both the interface between the oxide precipitate being SiO2 and the silicon matrix and the interface between the thermal oxide and silicon consist of a 2–3 nm thick SiO layer. As the results of these experiments also show that copper segregates at the SiO interface layer of the thermal oxide it is concluded that gettering of copper by oxide precipitates is based on segregation of copper to the SiO interface layer. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0151509jss] All rights reserved.
- Published
- 2015
39. Dislocation Generation and Propagation during Flash Lamp Annealing
- Author
-
Dawid Kot, Markus Andreas Schubert, Andreas Sattler, and Gudrun Kissinger
- Subjects
Flash-lamp ,dislocation ,Materials science ,Annealing (metallurgy) ,business.industry ,silicon ,Creative commons ,Dislocation free ,Electronic, Optical and Magnetic Materials ,yielding ,flash lamp annealing ,Optoelectronics ,Wafer ,Dislocation ,business - Abstract
Dislocation generation and propagation during flash lamp annealing for 20 ms was investigated using wafers with sawed, ground, and etched surfaces. Due to the thermal stress resulting from the temperature profiles generated by the flash pre-existing dislocations propagate into the wafer from both surfaces during flash lamp annealing. A dislocation free zone was observed around 700 μm depth below the surface of a 900 μm thick sawed wafer. The dislocation propagation can be well described by a three-dimensional mechanical model. It was further demonstrated that in wafers being initially free of dislocations no dislocations are generated during flash lamp annealing. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0151507jss] All rights reserved.
- Published
- 2015
40. A self-ordered, body-centered tetragonal superlattice of SiGe nanodot growth by reduced pressure CVD
- Author
-
Bernd Tillack, Roberto Bergamaschini, M Albani, Anne Hesse, Peter Zaumseil, Francesco Montalenti, Giovanni Capellini, Yuji Yamamoto, Markus Andreas Schubert, Thomas Schroeder, Yamamoto, Yuji, Zaumseil, Peter, Capellini, Giovanni, Andreas Schubert, Marku, Hesse, Anne, Albani, Marco, Bergamaschini, Roberto, Montalenti, Francesco, Schroeder, Thoma, Tillack, Bernd, Yamamoto, Y, Zaumseil, P, Capellini, G, Andreas Schubert, M, Hesse, A, Albani, M, Bergamaschini, R, Montalenti, F, Schroeder, T, and Tillack, B
- Subjects
Materials science ,Annealing (metallurgy) ,self-ordering ,SiGe ,Superlattice ,Bioengineering ,02 engineering and technology ,Chemical vapor deposition ,Epitaxy ,01 natural sciences ,Deposition temperature ,chemical vapor deposition ,Tetragonal crystal system ,0103 physical sciences ,Surface roughness ,General Materials Science ,Mechanics of Material ,Electrical and Electronic Engineering ,FIS/03 - FISICA DELLA MATERIA ,010302 applied physics ,Condensed matter physics ,Mechanical Engineering ,Chemistry (all) ,epitaxy ,General Chemistry ,nanodot ,021001 nanoscience & nanotechnology ,Mechanics of Materials ,Nanodot ,Materials Science (all) ,0210 nano-technology - Abstract
Self-ordered three-dimensional body-centered tetragonal (BCT) SiGe nanodot structures are fabricated by depositing SiGe/Si superlattice layer stacks using reduced pressure chemical vapor deposition. For high enough Ge content in the island (>30%) and deposition temperature of the Si spacer layers (T > 700 °C), we observe the formation of an ordered array with islands arranged in staggered position in adjacent layers. The in plane periodicity of the islands can be selected by a suitable choice of the annealing temperature before the Si spacer layer growth and of the SiGe dot volume, while only a weak influence of the Ge concentration is observed. Phase-field simulations are used to clarify the driving force determining the observed BCT ordering, shedding light on the competition between heteroepitaxial strain and surface-energy minimization in the presence of a non-negligible surface roughness.
- Published
- 2017
41. Impact of the precursor chemistry and process conditions on the cell-to-cell variability in 1T-1R based HfO
- Author
-
Alessandro, Grossi, Eduardo, Perez, Cristian, Zambelli, Piero, Olivo, Enrique, Miranda, Robin, Roelofs, Jacob, Woodruff, Petri, Raisanen, Wei, Li, Michael, Givens, Ioan, Costina, Markus Andreas, Schubert, and Christian, Wenger
- Subjects
Computer Storage Devices ,Hot Temperature ,Transistors, Electronic ,Photoelectron Spectroscopy ,Electric Conductivity ,Oxides ,Micro-Electrical-Mechanical Systems ,Models, Theoretical ,Carbon ,Article ,Oxygen ,Microscopy, Electron, Transmission ,X-Ray Diffraction ,Electric Impedance ,Crystallization ,Algorithms ,Hafnium - Abstract
The Resistive RAM (RRAM) technology is currently in a level of maturity that calls for its integration into CMOS compatible memory arrays. This CMOS integration requires a perfect understanding of the cells performance and reliability in relation to the deposition processes used for their manufacturing. In this paper, the impact of the precursor chemistries and process conditions on the performance of HfO2 based memristive cells is studied. An extensive characterization of HfO2 based 1T1R cells, a comparison of the cell-to-cell variability, and reliability study is performed. The cells’ behaviors during forming, set, and reset operations are monitored in order to relate their features to conductive filament properties and process-induced variability of the switching parameters. The modeling of the high resistance state (HRS) is performed by applying the Quantum-Point Contact model to assess the link between the deposition condition and the precursor chemistry with the resulting physical cells characteristics.
- Published
- 2017
42. Mechanism of the Key Impact of Residual Carbon Content on the Reliability of Integrated Resistive Random Access Memory Arrays
- Author
-
Christian Wenger, Piero Olivo, Ioan Costina, Xavier Cartoixà, Thomas Schroeder, Eduardo Perez, Markus Andreas Schubert, Gang Niu, Peter Zaumseil, Alessandro Grossi, and Cristian Zambelli
- Subjects
Work (thermodynamics) ,Materials science ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,01 natural sciences ,NO ,Reliability (semiconductor) ,0103 physical sciences ,Electronic ,Optical and Magnetic Materials ,Physical and Theoretical Chemistry ,Electrical conductor ,010302 applied physics ,Resistive touchscreen ,business.industry ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Resistive random-access memory ,Electronic, Optical and Magnetic Materials ,General Energy ,chemistry ,Optoelectronics ,Density functional theory ,0210 nano-technology ,business ,Carbon ,Random access - Abstract
Resistive random access memories (RRAM) require high density, low power consumption and high reliability. Systematic statistic electrical, material and theoretical studies were demonstrated in this work to point out and clarify a key impact of carbon residues on the resistive switching (RS), particularly the endurance, of the integrated HfO2-based 4 kbit RRAM array. The mechanism of the carbon atoms interacting with oxygen vacancies and serving also as filament was understood in nanoscale by performing density functional theory (DFT) calculations. Under an oxygen-deficient environment, carbon atoms tend to fill in oxygen vacancy (VO··) sites and could form conductive filaments which require higher energy to be broken compared to the original VO·· filaments. By controlling the residual carbon concentration lower than 4%, highly reliable HfO2-based integrated 4 kbit RRAM array was achieved, which is of great interest for future nonvolatile memories.
- Published
- 2017
43. Photoluminescence of phosphorus atomic layer doped Ge grown on Si
- Author
-
Yuji Yamamoto, Bernd Tillack, Markus Andreas Schubert, Winfried Seifert, Anne Hesse, Roger Loo, Giordano Scappucci, Giovanni Capellini, D. Sabbagh, Thomas Schroeder, Michele Virgilio, Junichi Murota, Ioan Costina, Li-Wei Nien, Ashwyn Srinivasan, Yamamoto, Yuji, Nien, Li wei, Capellini, Giovanni, Virgilio, Michele, Costina, Ioan, Schubert, Markus Andrea, Seifert, Winfried, Srinivasan, Ashwyn, Loo, Roger, Scappucci, Giordano, Sabbagh, Diego, Hesse, Anne, Murota, Junichi, Schroeder, Thoma, and Tillack, Bernd
- Subjects
Materials Chemistry2506 Metals and Alloys ,Materials science ,Photoluminescence ,Annealing (metallurgy) ,atomic layer doping ,chemical vapor deposition ,epitaxy ,gemanium ,phosporus ,photoluminescence ,Electronic, Optical and Magnetic Materials ,Condensed Matter Physics ,Electrical and Electronic Engineering ,Inorganic chemistry ,Analytical chemistry ,phosporu ,02 engineering and technology ,Chemical vapor deposition ,Condensed Matter Physic ,Epitaxy ,01 natural sciences ,Crystallinity ,0103 physical sciences ,Materials Chemistry ,Electronic ,Optical and Magnetic Materials ,010302 applied physics ,Materials Chemistry2506 Metals and Alloy ,Electronic, Optical and Magnetic Material ,Doping ,021001 nanoscience & nanotechnology ,Crystallographic defect ,0210 nano-technology ,Luminescence - Abstract
Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 Ã1013 cm-2 separated by 4 nm Ge spacer are selectively deposited at 300 °C on a 700 nm thick P-doped Ge buffer layer of 1.4 à 1019 cm-3 on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 à 1020 cm-3 with abrupt P delta profiles is formed by the P-ALD process. Compared to the P-doped Ge buffer layer, a reduced PL intensity is observed, which might be caused by a higher density of point defects in the P delta doped Ge layer. The peak position is shifted by â¼0.1 eV towards lower energy, indicating an increased active carrier concentration in the P-delta doped Ge layer. By introducing annealing at 400 °C to 500 °C after each Ge spacer deposition, P desorption and diffusion is observed resulting in relatively uniform P profiles of â¼2 à 1019 cm-3. Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.
- Published
- 2017
44. Heteroepitaxial growth of Ge on compliant strained nano-structured Si lines and dots on (001) silicon on insulator substrate
- Author
-
Thomas Schroeder, Peter Zaumseil, Yuji Yamamoto, Bernd Tillack, and Markus Andreas Schubert
- Subjects
Diffraction ,Materials science ,business.industry ,Metals and Alloys ,Silicon on insulator ,Surfaces and Interfaces ,Chemical vapor deposition ,Epitaxy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,Semiconductor ,Nano ,X-ray crystallography ,Materials Chemistry ,Optoelectronics ,Specular reflection ,business - Abstract
On the way to integrate lattice mismatched semiconductors on Si(001) we studied the Ge/Si heterosystem with the aim of a misfit dislocation free deposition that offers the vision to integrate defect-free alternative semiconductor structures on Si. Periodic Ge nano-structures (dots and lines) were selectively grown by chemical vapor deposition on Si nano-islands on silicon on insulator substrate with a thin (about 10 nm) SiGe buffer layer between Si and Ge. The strain state of the structures was measured by grazing incidence and specular diffraction using laboratory-based X-ray diffraction technique. The SiGe improves the compliance of the Si compared to direct Ge deposition, prevents plastic relaxation during growth, and allows elastic relaxation before Ge is deposited on top. As a result, an epitaxial growth of Ge on Si fully free of misfit dislocations was achieved.
- Published
- 2014
45. Selective Lateral Germanium Growth for Local GeOI Fabrication
- Author
-
Bernd Tillack, Yuji Yamamoto, Markus Andreas Schubert, and Christian Reich
- Subjects
Materials science ,Fabrication ,business.industry ,chemistry.chemical_element ,Germanium ,Epitaxy ,Thermal expansion ,Electronic, Optical and Magnetic Materials ,Root mean square ,chemistry ,Etching (microfabrication) ,Optoelectronics ,Wafer ,business ,Layer (electronics) - Abstract
High quality local Germanium-on-oxide (GeOI) wafers are fabricated using selective lateral germanium (Ge) growth technique by a single wafer reduced pressure chemical vapor deposition system. Mesa structures of 300 nm thick epitaxial silicon (Si) interposed by SiO2 cap and buried oxide are prepared. HCl vapor phase etching of Si is performed prior to selective Ge growth to remove a part of the epitaxial Si to form cavity under the mesa. By following selective Ge growth, the cavity was filled. Cross section TEM shows dislocations of Ge which are located near Si / Ge interface only. By plan view TEM, it is shown that the dislocations in Ge which direct to SiO2 cap or to buried-oxide (BOX) are located near the interface of Si and Ge. The dislocations which run parallel to BOX are observed only in [110] and [1–10] direction resulting Ge grown toward [010] direction contains no dislocations. This mechanism is similar to aspect-ratio-trapping but here we are using a horizontal approach, which offers the option to remove the defective areas by standard structuring techniques. A root mean square of roughness of ∼0.2 nm is obtained after the SiO2 cap removal. Tensile strain in the Ge layer is observed due to higher thermal expansion coefficient of Ge compared to Si and SiO2. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0071411jss] All rights reserved.
- Published
- 2014
46. Quantitative energy dispersive X-ray spectroscopy on thin SiGe layers
- Author
-
Markus Andreas Schubert, Peter Zaumseil, Ioan Costina, and Holger Rücker
- Published
- 2016
47. STEMEELS plasmon imaging (SEPI) for mixed phase silicon / silicon-oxides systems
- Author
-
Max Johann Klingsporn, Markus Andreas Schubert, Simon Kirner, Dawid Kot, Daniel Abou-Ras, Bernd Stannowski, and Gudrun Kissinger
- Published
- 2016
48. Reduction of Structural Defects in Ge Epitaxially Grown on Nano-Structured Si Islands on SOI Substrate
- Author
-
Peter Zaumseil, Markus Andreas Schubert, Thomas Schroeder, Bernd Tillack, and Yuji Yamamoto
- Subjects
Materials science ,Silicon ,business.industry ,Silicon on insulator ,chemistry.chemical_element ,Germanium ,Chemical vapor deposition ,Condensed Matter Physics ,Epitaxy ,Atomic and Molecular Physics, and Optics ,Crystallography ,Semiconductor ,chemistry ,Transmission electron microscopy ,Optoelectronics ,General Materials Science ,business ,Layer (electronics) - Abstract
One way to further increase performance and/or functionality of Si micro-and nanoelectronics is the integration of alternative semiconductors on silicon (Si). We studied the Ge/Si heterosystem with the aim to realize a Ge deposition free of misfit dislocations and with low content of other structural defects. Ge nanostructures were selectively grown by chemical vapor deposition on periodic Si nanoislands (dots and lines) on SOI substrate either directly or with a thin (about 10 nm) SiGe buffer layer. The strain state of the structures was measured by different laboratory-based x-ray diffraction techniques. It was found that a suited SiGe buffer improves the compliance of the Si compared to direct Ge deposition; plastic relaxation during growth can be prevented, and fully elastic relaxation of the structure can be achieved. Transmission electron microscopy confirms that the epitaxial growth of Ge on nanostructured Si is free of misfit dislocations.
- Published
- 2013
49. Influence of Cu Concentration on the Getter Efficiency of Dislocations and Oxygen Precipitates in Silicon Wafers
- Author
-
Gudrun Kissinger, Markus Andreas Schubert, Timo Müller, Dawid Kot, and Andreas Sattler
- Subjects
Materials science ,Silicon ,Annealing (metallurgy) ,Metallurgy ,chemistry.chemical_element ,Atmospheric temperature range ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Oxygen precipitates ,chemistry ,Getter ,General Materials Science ,Wafer ,Dislocation - Abstract
Two getter tests were carried out in order to study the getter efficiency of oxygen precipitates in silicon samples contaminated with low and high Cu concentration. The samples were pre-treated by RTA followed by annealing in the temperature range between 700 °C and 1000 °C for various times in order to establish different concentrations and different sizes of oxygen precipitates in the samples. From the analysis of the results of the normalized inner surface and the gettering efficiency, it was deduced that in highly contaminated samples Cu precipitates more easily at dislocations than at the surface of oxygen precipitates. Contrarily, in the samples contaminated with low Cu concentration the presence of dislocations does not improve the getter efficiency. Cu precipitates were found at the edge of a plate-like precipitate in a sample with low Cu concentration.
- Published
- 2013
50. X-ray characterization of Ge dots epitaxially grown on nanostructured Si islands on silicon-on-insulator substrates
- Author
-
Peter Zaumseil, Markus Andreas Schubert, Thomas Schroeder, Grzegorz Kozlowski, and Yuji Yamamoto
- Subjects
Diffraction ,Materials science ,business.industry ,Ge heteroepitaxy ,technology, industry, and agriculture ,X-ray ,Silicon on insulator ,Nanotechnology ,Chemical vapor deposition ,Epitaxy ,nanostructured Si ,grazing-incidence X-ray diffraction ,General Biochemistry, Genetics and Molecular Biology ,Nanoclusters ,Semiconductor ,Transmission electron microscopy ,transmission electron microscopy (TEM) ,silicon-on-insulator (SOI) substrates ,Optoelectronics ,X-Ray Diffraction and Imaging ,business - Abstract
Selective epitaxial growth of Ge on nanostructured Si islands on silicon-on-insulator substrates is investigated by X-ray diffraction and transmission electron microscopy to prove the compliance effect between the materials and the structural perfection, especially under the use of a thin SiGe buffer layer., On the way to integrate lattice mismatched semiconductors on Si(001), the Ge/Si heterosystem was used as a case study for the concept of compliant substrate effects that offer the vision to be able to integrate defect-free alternative semiconductor structures on Si. Ge nanoclusters were selectively grown by chemical vapour deposition on Si nano-islands on silicon-on-insulator (SOI) substrates. The strain states of Ge clusters and Si islands were measured by grazing-incidence diffraction using a laboratory-based X-ray diffraction technique. A tensile strain of up to 0.5% was detected in the Si islands after direct Ge deposition. Using a thin (∼10 nm) SiGe buffer layer between Si and Ge the tensile strain increases to 1.8%. Transmission electron microscopy studies confirm the absence of a regular grid of misfit dislocations in such structures. This clear experimental evidence for the compliance of Si nano-islands on SOI substrates opens a new integration concept that is not only limited to Ge but also extendable to semiconductors like III–V and II–VI materials.
- Published
- 2013
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