27 results on '"Markus Andreas Schubert"'
Search Results
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. 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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6. 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
7. 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
8. 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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9. 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
10. Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back
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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
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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.
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- 2018
11. Mechanism of the Key Impact of Residual Carbon Content on the Reliability of Integrated Resistive Random Access Memory Arrays
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Christian Wenger, Piero Olivo, Ioan Costina, Xavier Cartoixà, Thomas Schroeder, Eduardo Perez, Markus Andreas Schubert, Gang Niu, Peter Zaumseil, Alessandro Grossi, and Cristian Zambelli
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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.
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- 2017
12. Photoluminescence of phosphorus atomic layer doped Ge grown on Si
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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
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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.
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- 2017
13. Dislocation-free Ge Nano-crystals via Pattern Independent Selective Ge Heteroepitaxy on Si Nano-Tip Wafers
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Tore Niermann, Peter Zaumseil, Thomas Schroeder, Ya-Hong Xie, Gang Niu, Jens Katzer, Giovanni Capellini, Hans von Känel, Markus Andreas Schubert, Oliver Skibitzki, Michael Lehmann, H. M. Krause, Niu, Gang, Capellini, Giovanni, Schubert, Markus Andrea, Niermann, Tore, Zaumseil, Peter, Katzer, Jen, Krause, Hans Michael, Skibitzki, Oliver, Lehmann, Michael, Xie, Ya Hong, Von Känel, Han, and Schroeder, Thomas
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Materials science ,Thermodynamic equilibrium ,Nucleation ,Bioengineering ,02 engineering and technology ,Chemical vapor deposition ,01 natural sciences ,Article ,0103 physical sciences ,Nano ,Nanotechnology ,Wafer ,Structural properties ,Quantum dots ,010302 applied physics ,Multidisciplinary ,business.industry ,021001 nanoscience & nanotechnology ,Other Physical Sciences ,Quantum dot ,Optoelectronics ,Nanometre ,Biochemistry and Cell Biology ,0210 nano-technology ,business ,Molecular beam epitaxy - Abstract
The integration of dislocation-free Ge nano-islands was realized via selective molecular beam epitaxy on Si nano-tip patterned substrates. The Si-tip wafers feature a rectangular array of nanometer sized Si tips with (001) facet exposed among a SiO2 matrix. These wafers were fabricated by complementary metal-oxide-semiconductor (CMOS) compatible nanotechnology. Calculations based on nucleation theory predict that the selective growth occurs close to thermodynamic equilibrium, where condensation of Ge adatoms on SiO2 is disfavored due to the extremely short re-evaporation time and diffusion length. The growth selectivity is ensured by the desorption-limited growth regime leading to the observed pattern independence, i.e. the absence of loading effect commonly encountered in chemical vapor deposition. The growth condition of high temperature and low deposition rate is responsible for the observed high crystalline quality of the Ge islands which is also associated with negligible Si-Ge intermixing owing to geometric hindrance by the Si nano-tip approach. Single island as well as area-averaged characterization methods demonstrate that Ge islands are dislocation-free and heteroepitaxial strain is fully relaxed. Such well-ordered high quality Ge islands present a step towards the achievement of materials suitable for optical applications., Scientific Reports, 6, ISSN:2045-2322
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- 2016
14. Misfit dislocation free epitaxial growth of SiGe on compliant nanostructured silicon
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Markus Andreas Schubert, Yuji Yamamoto, Peter Zaumseil, Giovanni Capellini, Thomas Schroeder, Oliver Skibitzki, Zaumseil, Peter, Schubert, Markus Andrea, Yamamoto, Yuji, Skibitzki, Oliver, Capellini, Giovanni, and Schroeder, Thomas
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Nanostructure ,Materials science ,Atomic and Molecular Physics, and Optic ,Silicon ,business.industry ,SiGe ,XRD ,chemistry.chemical_element ,Germanium ,Epitaxy ,Condensed Matter Physics ,Nano-structured Si ,Atomic and Molecular Physics, and Optics ,Heteroepitaxy ,Crystallography ,chemistry ,Transmission electron microscopy ,Nano ,TEM ,Optoelectronics ,Microelectronics ,General Materials Science ,Materials Science (all) ,business ,Nanopillar - Abstract
The integration of germanium (Ge) into silicon-based microelectronics technologies is currently attracting increasing interest and research effort. One way to realize this without threading and misfit dislocations is the so-called nanoheteroepitaxy approach. We demonstrate that a modified Si nanostructure approach with nanopillars or bars separated by TEOS SiO2 can be used successfully to deposit SiGe dots and lines free of misfit dislocations. It was found that strain relaxation in the pseudomorphically grown SiGe happens fully elastically. These studies are important for the understanding of the behavior of nanostructured Si for the final goal of Ge integration via SiGe buffer.
- Published
- 2016
15. Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition
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Gang Niu, Hee-Dong Kim, Robin Roelofs, Eduardo Perez, Markus Andreas Schubert, Peter Zaumseil, Ioan Costina, and Christian Wenger
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Titanium ,structural properties ,Computer Storage Devices ,Hot Temperature ,Silicones ,Oxides ,Equipment Design ,Article ,Electrical and electronic engineering ,Semiconductors ,information storage ,Electric Impedance ,electronic and spintronic devices ,Hafnium - Abstract
With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.
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- 2016
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16. Sn migration control at high temperature due to high deposition speed for forming high-quality GeSn layer
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Giovanni Capellini, Wolfgang M. Klesse, Dan Buca, Noriyuki Taoka, Michele Montanari, Markus Andreas Schubert, Peter Zaumseil, Nils von den Driesch, Thomas Schroeder, Taoka, Noriyuki, Capellini, Giovanni, Von Den Driesch, Nil, Buca, Dan, Zaumseil, Peter, Schubert, Markus Andrea, Klesse, Wolfgang Matthia, Montanari, Michele, and Schroeder, Thomas
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010302 applied physics ,Photoluminescence ,Materials science ,Precipitation (chemistry) ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Crystallinity ,Physics and Astronomy (all) ,Quality (physics) ,Engineering (all) ,0103 physical sciences ,0210 nano-technology ,Deposition (chemistry) ,Layer (electronics) - Abstract
A key factor for controlling Sn migration during GeSn deposition at a high temperature of 400 °C was investigated. Calculated results with a simple model for the Sn migration and experimental results clarified that low-deposition-speed (v d) deposition with v d’s of 0.68 and 2.8 nm/min induces significant Sn precipitation, whereas high-deposition-speed (v d = 13 nm/min) deposition leads to high crystallinity and good photoluminescence spectrum of the GeSn layer. These results indicate that v d is a key parameter, and that control of Sn migration at a high temperature is possible. These results are of great relevance for the application of high-quality Sn-based alloys in future optoelectronics devices.
- Published
- 2016
17. Reduced-Pressure Chemical Vapor Deposition Growth of Isolated Ge Crystals and Suspended Layers on Micrometric Si Pillars
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Oliver Skibitzki, Andrea Ballabio, Thomas Schroeder, Giovanni Capellini, Peter Zaumseil, Markus Andreas Schubert, Marco Salvalaglio, Yuji Yamamoto, Roberto Bergamaschini, Francesco Montalenti, Leo Miglio, Skibitzki, O, Capellini, G, Yamamoto, Y, Zaumseil, P, Schubert, M, Schroeder, T, Ballabio, A, Bergamaschini, R, Salvalaglio, M, Miglio, L, Montalenti, F, Skibitzki, Oliver, Capellini, Giovanni, Yamamoto, Yuji, Zaumseil, Peter, Schubert, Markus Andrea, Schroeder, Thoma, Ballabio, Andrea, Bergamaschini, Roberto, Salvalaglio, Marco, Miglio, Leo, and Montalenti, Francesco
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Diffraction ,reduced pressure chemical vapor deosition ,Materials science ,vertical heteroepitaxy ,chemistry.chemical_element ,Nanotechnology ,Germanium ,02 engineering and technology ,Chemical vapor deposition ,dislocations ,germanium ,growth dynamics simulation ,patterned Si ,selective growth ,virtual substrate ,Materials Science (all) ,Epitaxy ,01 natural sciences ,0103 physical sciences ,General Materials Science ,Spectroscopy ,FIS/03 - FISICA DELLA MATERIA ,010302 applied physics ,dislocation ,Reduced pressure chemical vapor deposition ,021001 nanoscience & nanotechnology ,Highly selective ,reduced pressure chemical vapor deposition ,chemistry ,Chemical engineering ,Transmission electron microscopy ,0210 nano-technology - Abstract
In this work, we demonstrate the growth of Ge crystals and suspended continuous layers on Si(001) substrates deeply patterned in high aspect-ratio pillars. The material deposition was carried out in a commercial reduced-pressure chemical vapor deposition reactor, thus extending the "vertical-heteroepitaxy" technique developed by using the peculiar low-energy plasma-enhanced chemical vapor deposition reactor, to widely available epitaxial tools. The growth process was thoroughly analyzed, from the formation of small initial seeds to the final coalescence into a continuous suspended layer, by means of scanning and transmission electron microscopy, X-ray diffraction, and μ-Raman spectroscopy. The preoxidation of the Si pillar sidewalls and the addition of hydrochloric gas in the reactants proved to be key to achieve highly selective Ge growth on the pillars top only, which, in turn, is needed to promote the formation of a continuous Ge layer. Thanks to continuum growth models, we were able to single out the different roles played by thermodynamics and kinetics in the deposition dynamics. We believe that our findings will open the way to the low-cost realization of tens of micrometers thick heteroepitaxial layer (e.g., Ge, SiC, and GaAs) on Si having high crystal quality.
- Published
- 2016
18. Synthesis of graphene-like transparent conductive films on dielectric substrates using a modified filtered vacuum arc system
- Author
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Markus Andreas Schubert, Peter Siemroth, Paolo Prosposito, Mauro Casalboni, Helge Lux, Sigurd Schrader, and Anna Sgarlata
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Argon ,Materials science ,business.industry ,Graphene ,General Physics and Astronomy ,chemistry.chemical_element ,Vacuum arc ,law.invention ,Settore FIS/03 - Fisica della Materia ,symbols.namesake ,Optics ,chemistry ,law ,symbols ,Sapphire ,Optoelectronics ,ddc:621 ,Scanning tunneling microscope ,Raman spectroscopy ,business ,Silicon oxide ,Sheet resistance - Abstract
Here, we present a reliable process to deposit transparent conductive films on silicon oxide, quartz, and sapphire using a solid carbon source. This layer consists of partially ordered graphene flakes with a lateral dimension of about 5 nm. The process does not require any catalytic metal and exploits a high current arc evaporation (Φ-HCA) to homogeneously deposit a layer of carbon on heated substrates. A gas atmosphere consisting of Argon or Argon/Hydrogen blend acting as a buffer influences the morphology of the growing film. scanning tunneling microscopy, transmission electron microscopy, and Raman spectra were used for a thorough characterization of the samples in order to optimize the growth parameters. The best carbon layers have a surface resistance of 5.7 × 103 Ω◻ whereas the optical transparency of the coatings is 88% with an excellent homogeneity over areas of several cm2. Such results are compatible with most semiconductor fabrication processes and make this method very promising for various industrial applications.
- Published
- 2015
19. On the local electronic and atomic structure of Ce1-xPrxO2-delta epitaxial films on Si
- Author
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Federico Boscherini, Francesco d'Acapito, Marvin Hartwig Zoellner, Thomas Schroeder, Gang Niu, Markus Andreas Schubert, Niu, G., Schubert, M.A., D'Acapito, F., Zoellner, M.H., Schroeder, T., and Boscherini, F.
- Subjects
Valence (chemistry) ,Materials science ,Absorption spectroscopy ,Extended X-ray absorption fine structure ,Photoemission spectroscopy ,synchrotron radiation ,Analytical chemistry ,General Physics and Astronomy ,Electronic structure ,XANES ,Crystallography ,thin films ,Scanning transmission electron microscopy ,oxide ,Spectroscopy - Abstract
The local electronic and atomic structure of (111)-oriented, single crystalline mixed Ce1-xPrxO2-delta (x = 0, 0.1 and 0.6) epitaxial thin films on silicon substrates have been investigated in view of engineering redox properties of complex oxide films. Non-destructive X-ray absorption near edge structure reveals that Pr shows only +3 valence and Ce shows only nominal +4 valence in mixed oxides. Extended x-ray absorption fine structure (EXAFS) studies were performed at K edges of Ce and Pr using a specially designed monochromator system for high energy measurements. They demonstrate that the fluorite lattice of ceria (CeO2) is almost not perturbed for x = 0.1 sample, while higher Pr concentration (x = 0.6) not only generates a higher disorder level (thus more disordered oxygen) but also causes a significant reduction of Ce-O interatomic distances. The valence states of the cations were also examined by techniques operating in highly reducing environments: scanning transmission electron microscopy-electron energy loss spectroscopy and X-ray photoemission spectroscopy; in these reducing environments, evidence for the presence of Ce3+ was clearly found for the higher Pr concentration. Thus, the introduction of Pr3+ into CeO2 strongly enhances the oxygen exchange properties of CeO2. This improved oxygen mobility properties of CeO2 are attributed to the lattice disorder induced by Pr mixing in the CeO2 fluorite lattice, as demonstrated by EXAFS measurements. Thus, a comprehensive picture of the modifications of the atomic and electronic structure of Ce1-xPrxO2-delta epitaxial films and their relation is obtained. (C) 2014 AIP Publishing LLC.
- Published
- 2014
20. Graphene Grown on Ge(001) from Atomic Source
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Grzegorz Lupina, Jarek Dąbrowski, Yuji Yamamoto, Gunther Lippert, Felix Herziger, Markus Andreas Schubert, Christoph Tegenkamp, José Avila, Thomas Schroeder, Jens Baringhaus, Maria C. Asensio, and Janina Maultzsch
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Materials science ,FOS: Physical sciences ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,law.invention ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Microelectronics ,General Materials Science ,Wafer ,Sheet resistance ,Surface diffusion ,Condensed Matter - Mesoscale and Nanoscale Physics ,business.industry ,Graphene ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Semiconductor ,chemistry ,Optoelectronics ,Density functional theory ,0210 nano-technology ,business ,Carbon - Abstract
Among the many anticipated applications of graphene, some - such as transistors for Si microelectronics - would greatly benefit from the possibility to deposit graphene directly on a semiconductor grown on a Si wafer. We report that Ge(001) layers on Si(001) wafers can be uniformly covered with graphene at temperatures between 800{\deg}C and the melting temperature of Ge. The graphene is closed, with sheet resistivity strongly decreasing with growth temperature, weakly decreasing with the amount of deposited C, and reaching down to 2 kOhm/sq. Activation energy of surface roughness is low (about 0.66 eV) and constant throughout the range of temperatures in which graphene is formed. Density functional theory calculations indicate that the major physical processes affecting the growth are: (1) substitution of Ge in surface dimers by C, (2) interaction between C clusters and Ge monomers, and (3) formation of chemical bonds between graphene edge and Ge(001), and that the processes 1 and 2 are surpassed by CH$_{2}$ surface diffusion when the C atoms are delivered from CH$_{4}$. The results of this study indicate that graphene can be produced directly at the active region of the transistor in a process compatible with the Si technology.
- Published
- 2013
21. (Invited) Nickel and Nickel-Platinum Silicide for BiCMOS Devices
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Marvin Zöllner, Jean-Paul Blaschke, Holger Rücker, Bernd Heinemann, Thomas Grabolla, Markus Andreas Schubert, Thomas Lenke, Dan Deyo, Jürgen Drews, Heinz-Peter Stoll, Sebastian Schulze, Dirk Wolansky, and Uwe Richter
- Subjects
Platinum silicide ,chemistry.chemical_compound ,Nickel ,Materials science ,chemistry ,0502 economics and business ,05 social sciences ,Metallurgy ,chemistry.chemical_element ,050207 economics ,BiCMOS ,7. Clean energy - Abstract
Recently, the world’s fastest SiGe-HBT was presented by IHP researchers [1], which applies low ohmic nickel silicide (NiSi). Among other measures, this feature contributed to speed improvements. On the other hand, the integration of low-ohmic NiSi creates the risk for NiSi defects which could result in increased MOSFET leakage currents. The goal of this contribution is to find out from several two-step silicidations of Ni or NiPt layers a suitable process for a BiCMOS technology which enables low silicide RS for high cutoff frequencies of bipolar and MOS transistors without degradation of leakage currents. In result, a 300°C/450°C silicidation is proposed providing RS values of 3 to 4 Ω for both NiSi and NiPtSi. However, only the NiPtSi shows acceptable low leakage currents compared to NiSi. Therefore, NiPt extends the silicide process window for HBTs and MOSFETs. The phase transitions of Ni and NiPt silicides as a function of temperature are shown in Fig. 1, where the temperature range of the targeted NiSi phase is enlarged for NiPt compared to Ni. The investigated two-step NiSi formations are listed in Table 1. The NiPt layers were deposited in an Applied Materials laboratory. First, Ni2Si was formed by furnace anneal, low pressure anneals, or by a NiPt sputtering at 400°C. The Ni rich silicide was converted into NiSi by a second anneal at 450°C. The final Ni(Pt)Si sheet resistance (RS Ni(Pt)Si:1.+2.Ann) was tunable from 1.5 Ω to 10.5 Ω by the temperature and time of the first anneal (Fig. 2). At 300°C, the RS saturates at 3.3 Ω for 20 nm Ni and 1.6 Ω for 40 nm Ni, respectively. This indicates full Ni consumption. The furnace anneals at 200°C and 230°C do not show any RS saturation since Ni is consumed only partially. An RS increase for NiSi and NiPtSi on PSD (p source-drain) compared to NiSi on substrate is observed. One figure of merit of SiGe-HBTs is the maximum oscillation frequency fmax, which depends by the following equation fmax=sqrt(fT/(8πrBcBC)) on the transit frequency fT, the base resistance rB, and the collector-base capacitance cBC. A silicide resistance variation could mainly influence rB. In Fig. 3a, the sheet resistance of the silicided base polysilicon (RS BasePolySilicide) together with fmax of two HBT layouts are plotted for several silicide formations. It exists a correlation between fmax and RS BasePolySilicide, which is shown in Fig. 3b. In general, fmax could be enlarged by a silicide resistance reduction for special HBT layouts. For these low-ohmic and thick Ni(Pt)Si layers, special attention has to be paid to the MOSFET leakage currents, which can be enlarged by lateral silicide pipes towards the conducting channel or by defects along the SD – STI (shallow trench isolation) interface [2]. Another leakage current source are silicide spikes shortening in a perpendicular direction the SD and the well. Three types of P+Nwell and N+Pwell diodes are suitable to determine and distinguish these silicide based yield killers: area diodes to detect spikes, STI separated island diodes to recognize SD-STI defects, and diodes with long poly-gates on SD-well areas to determine pipes at gate edges. In result, the area and island diodes showed no leakage current increase for the studied silicidations, i.e. defects along the SD-STI edge and spikes are not critical here. The leakage currents of gate-edged diodes on N+Pwell and P+Nwell are presented in Fig.4. Both diode types show low leakage currents for the 200°C and 230°C anneals, because the low lateral silicidation at these temperatures reduces the probability for piping. At 300° the N+Pwell leakage current increases slightly up to 2x10-9A, but significantly up to 1x10-7A for the P+Nwell diode. This is a clear indication for pipes at the gate edges [3]. In contrast, almost no enhanced leakage current was observed for the NiPt silicidations with 200° to 300°C anneals. The pipe suppression of the NiPt silicide system might be caused by the Pt agglomeration at the silicide-SD interface [4]. The limits of the NiPt pipe suppression are shown for N+Pwell diodes silicidated with a NiPt deposition at 400°C. Leakage currents of 1x10-8A could indicate NMOS-typical pipes, as described by Yamaguchi [5]. In summary, silicide layers with low RS values of 3Ω to 4Ω were formed by two-step annealing of Ni and NiPt at 300°C and 450°C. These silicides support high fmax values of SiGe HBTs. However, only the NiPt silicide process provided acceptable low leakage currents of MOSFET test structures indicating an extended process capability of NiPtSi compared to NiSi. Figure 1
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22. Ge/SiGe multiple quantum well fabrication by reduced-pressure chemical vapor deposition.
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Yuji Yamamoto, Oliver Skibitzki, Markus Andreas Schubert, Mario Scuderi, Felix Reichmann, Marvin H. Zöllner, Monica De Seta, Giovanni Capellini, and Bernd Tillack
- Abstract
In this paper we deposit structures comprising a stack of 10 periods made of 15-nm-thick Ge multiple quantum wells (MQWs) enclosed in a 15-nm-thick Si
0.2 Ge0.8 barrier on SiGe virtual substrates (VSs) featuring different Ge content in the 85%–100% range to investigate the influence of heteroepitaxial strain on Si0.2 Ge0.8 and Ge growth. With increasing Ge concentration of the VS, the growth rate of Si0.2 Ge0.8 in the MQWs increases. Si incorporation into the Si0.2 Ge0.8 layer also becomes slightly higher. However, almost no influence of the growth rate is observed for Ge growth in the MQWs. We argue that increased tensile strain promotes the Si reaction at the surface. In the case of Si0.2 Ge0.8 growth on Ge, we observe a smeared interface due to Ge segregation during the growth. Furthermore, we observe that the interface width increases with increasing Ge concentration of the VS. We attribute this observation to the increased segregation of Ge driven by increased strain energy accumulated in the Si0.2 Ge0.8 layers. We also observe that the MQW layer “filters out” threading dislocations formed in the VS. [ABSTRACT FROM AUTHOR]- Published
- 2020
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23. Influence of annealing conditions on threading dislocation density in Ge deposited on Si by reduced pressure chemical vapor deposition.
- Author
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Yuji Yamamoto, Peter Zaumseil, Markus Andreas Schubert, and Bernd Tillack
- Subjects
ANNEALING of metals ,ELECTRIC properties of germanium ,DISLOCATIONS in metals ,CHEMICAL vapor deposition ,CRYSTALLINITY ,CRYSTAL growth - Abstract
The influence of annealing conditions on the crystallinity of Ge deposited on Si(001) is investigated. Ge deposited with postannealing at 800 °C and 850 °C, five cycles of postannealing at 750 °C and 850 °C (temperature-swing postannealing) and several cycles of annealing at 800 °C or 850 °C during the Ge growth by interrupting the deposition step (cyclic annealing) are compared. To check the threading dislocation density (TDD) of the deeper part of the Ge, thinning by HCl vapor phase etching (VPE) followed by Secco defect etching is performed for 5 μm thick Ge of all three annealing variants. By comparing the TDD of the same Ge thickness with and without HCl VPE, TDD reduction by VPE is observed for the sample using the cyclic annealing process only. Lower TDD is observed at higher postannealing temperature. By the five cycles of temperature swinging, TDD becomes around a half compared to conventional postannealing at 850 °C. In the case of the cyclic annealing process significant improvement of TDD is observed with increasing Ge thickness. Even at a maximum temperature of 800 °C, the same or lower TDD levels were observed for higher than 2 μm thick Ge compared to that with five cycles of temperature-swing postannealing. For the sample with cyclic annealing at 800 °C, a lower Si diffusion length into Ge is also observed for the cyclic annealing process indicating a lower thermal budget. A lower amount of tilted Ge planes at the interface is confirmed showing higher crystal quality also in the deeper part of the Ge layer. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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24. Alignment control of self-ordered three dimensional SiGe nanodots.
- Author
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Yuji Yamamoto, Yuhki Itoh, Peter Zaumseil, Markus Andreas Schubert, Giovanni Capellini, Francesco Montalenti, Katsuyoshi Washio, and Bernd Tillack
- Subjects
SEMICONDUCTOR quantum dots ,OPTICAL properties of nanostructured materials ,CHEMICAL vapor deposition ,SURFACE energy ,SILICON alloys ,SEMICONDUCTOR technology - 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 SiH
4 -GeH4 at 550 °C and SiH4 or SiH2 Cl2 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 SiH2 Cl2 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. [ABSTRACT FROM AUTHOR]- Published
- 2018
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25. Photoluminescence from GeSn nano-heterostructures.
- Author
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Viktoria Schlykow, Peter Zaumseil, Markus Andreas Schubert, Oliver Skibitzki, Yuji Yamamoto, Wolfgang Matthias Klesse, Yaonan Hou, Michele Virgilio, Monica De Seta, Luciana Di Gaspare, Thomas Schroeder, and Giovanni Capellini
- Subjects
PHOTOLUMINESCENCE ,GERMANIUM compounds ,HETEROSTRUCTURES - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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26. A self-ordered, body-centered tetragonal superlattice of SiGe nanodot growth by reduced pressure CVD.
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Yuji Yamamoto, Peter Zaumseil, Giovanni Capellini, Markus Andreas Schubert, Anne Hesse, Marco Albani, Roberto Bergamaschini, Francesco Montalenti, Thomas Schroeder, and Bernd Tillack
- Subjects
SILICON compounds ,SUPERLATTICES ,CHEMICAL vapor deposition - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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27. Sn migration control at high temperature due to high deposition speed for forming high-quality GeSn layer.
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Noriyuki Taoka, Giovanni Capellini, Nils von den Driesch, Dan Buca, Peter Zaumseil, Markus Andreas Schubert, Wolfgang Matthias Klesse, Michele Montanari, and Thomas Schroeder
- Abstract
A key factor for controlling Sn migration during GeSn deposition at a high temperature of 400 °C was investigated. Calculated results with a simple model for the Sn migration and experimental results clarified that low-deposition-speed (v
d ) deposition with vd ’s of 0.68 and 2.8 nm/min induces significant Sn precipitation, whereas high-deposition-speed (vd = 13 nm/min) deposition leads to high crystallinity and good photoluminescence spectrum of the GeSn layer. These results indicate that vd is a key parameter, and that control of Sn migration at a high temperature is possible. These results are of great relevance for the application of high-quality Sn-based alloys in future optoelectronics devices. [ABSTRACT FROM AUTHOR]- Published
- 2016
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