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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.

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.

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.

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.

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.]

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.

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).

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).

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.

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.

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.

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.

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.

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)

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.

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.

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.

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.

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.

Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 ×1013 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 × 1019 cm-3 on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 × 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 ∼0.1 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 ∼2 × 1019 cm-3. Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.

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.

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.

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.

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.

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.

We present a photonic BiCMOS process enabling for monolithically integrated Si-based transceiver front-ends towards single-wavelength 400 Gb/s data rate by combining segmented Mach-Zehnder-Interferometer modulators and high-speed germanium photo detectors with high-performance electronics.

The epitaxial integration of highly heterogeneous material systems with silicon (Si) is a central topic in (opto-)electronics owing to device applications. InP could open new avenues for the realization of novel devices such as high-mobility transistors in next-generation CMOS or efficient lasers in Si photonics circuitry. However, the InP/Si heteroepitaxy is highly challenging due to the lattice (∼8%), thermal expansion mismatch (∼84%), and the different lattice symmetries. Here, we demonstrate the growth of InP nanocrystals showing high structural quality and excellent optoelectronic properties on Si. Our CMOS-compatible innovative approach exploits the selective epitaxy of InP nanocrystals on Si nanometric seeds obtained by the opening of lattice-arranged Si nanotips embedded in a SiO2 matrix. A graphene/InP/Si-tip heterostructure was realized on obtained materials, revealing rectifying behavior and promising photodetection. This work presents a significant advance toward the monolithic integration of graphene/III-V based hybrid devices onto the mainstream Si technology platform.

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

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.

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.

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.

The influence of RTA pre-treatments on the morphology of oxygen precipitates in silicon wafers as deduced from haze getter tests was confirmed by FTIR and TEM investigations. Based on the results of the getter tests, the ratio between the density of plate-like and octahedral precipitates was calculated for RTA pre-treated silicon samples.

The selective epitaxial growth of germanium on nano-structured periodic silicon pillars and bars with 360 nm periodicity on Si(001) substrate is studied to evaluate the applicability of nano-heteroepitaxy on the Ge–Si system for different fields of application. It is found that SiO 2 used as masking material plays the key role to influence the strain situation in the Si nano-islands. To analyze this in detail, X-ray diffraction techniques in combination with theoretical simulations based on the kinematical X-ray scattering from laterally strained nano-structures and finite element method (FEM) calculations of the strain field are applied. The oxide related strain in the Si scales about linearly with the thickness of the SiO 2 mask, but FEM simulations supposing a homogeneous stress distribution in the oxide are not sufficient to describe the local strain distribution in the nano-structures. It is demonstrated that the Ge lattice relaxes completely during growth on the Si nano-islands by generation of misfit dislocations at the interface, but a high structural quality of Ge can be achieved by suited growth conditions.

The solid phase epitaxy (SPE) of undoped amorphous Si (a-Si) deposited on SiO2 patterned Si(001) wafers by reduced pressure chemical vapor deposition (RPCVD) using a H2–Si2H6 gas system was investigated. The SPE was performed by applying in-situ postannealing directly after deposition process. By transmission electron microscopy (TEM) and scanning electron microscopy, we studied the lateral SPE (L-SPE) length on sidewall and mask for various postannealing times, temperatures and a-Si thicknesses. We observed an increase in L-SPE growth for longer postannealing times, temperatures and larger Si thicknesses on mask. TEM defect studies revealed that by SPE crystallized epi-Si exhibits a higher defect density on the mask than at the inside of the mask window. By introducing SiO2-cap on the sample with 180 nm Si thickness following postannealing at 570 °C for 5 h, the crystallization of up to 450 nm epi-Si from a-Si is achieved. We demonstrated the possibility to use this technique for SiGe:C heterojunction bipolar transistor (HBT) base layer stack to crystallize Si-buffer layer to widen the monocrystalline region around the bipolar window and to improve base link resistivity of the HBT.

Dislocation networks are one of the most principle sources deteriorating the performances of devices based on lattice-mismatched heteroepitaxial systems. We demonstrate here a technique enabling fully coherent germanium (Ge) islands selectively grown on nanotip-patterned Si(001) substrates. The silicon (Si)-tip-patterned substrate, fabricated by complementary metal oxide semiconductor compatible nanotechnology, features ∼50-nm-wide Si areas emerging from a SiO2 matrix and arranged in an ordered lattice. Molecular beam epitaxy growths result in Ge nanoislands with high selectivity and having homogeneous shape and size. The ∼850 °C growth temperature required for ensuring selective growth has been shown to lead to the formation of Ge islands of high crystalline quality without extensive Si intermixing (with 91 atom % Ge). Nanotip-patterned wafers result in geometric, kinetic-diffusion-barrier intermixing hindrance, confining the major intermixing to the pedestal region of Ge islands, where kinetic diffusion barriers are, however, high. Theoretical calculations suggest that the thin Si/Ge layer at the interface plays, nevertheless, a significant role in realizing our fully coherent Ge nanoislands free from extended defects especially dislocations. Single-layer graphene/Ge/Si-tip Schottky junctions were fabricated, and thanks to the absence of extended defects in Ge islands, they demonstrate high-performance photodetection characteristics with responsivity of ∼45 mA W(-1) and an Ion/Ioff ratio of ∼10(3).

Solid-phase epitaxy (SPE) of in situ As-doped amorphous Si (a-Si) deposited on SiO 2 /Si 3 N 4 patterned Si (1 0 0) wafers by reduced pressure chemical vapour deposition (RPCVD) using a H 2 –Si 2 H 6 gas system was investigated. The SPE was performed by applying in situ postannealing directly after deposition process. On the one hand, we studied the lateral SPE (L-SPE) length of As-doped Si on mask and their crystal quality by TEM/SEM characterisation for various postannealing temperatures (700–1000 °C for 60 s). We observed increase in L-SPE growth and decrease of dislocation density for higher postannealing temperatures. On the other hand, L-SPE length was also investigated for different postannealing times (0–120 min at 575 °C) and As concentrations. At these conditions the L-SPE length has increased with increasing postannealing time. For both, higher and lower annealing temperature region, crystallization has been inhibited for higher As concentrations. After modifying As-doping level, we were able to crystallize up to 500 nm of a-Si on mask to epi-Si by combination of 575 °C and 1000 °C postannealing.

A 0.13 μm SiGe BiCMOS technology for millimeter-wave applications is presented. This technology features high-speed HBTs with peak transit frequencies fT of 240 GHz, maximum oscillation frequencies fmax of 330 GHz, and breakdown voltages BVCEO of 1.7 V along with high-voltage HBTs (fT = 50 GHz,fmax = 130 GHz, BVCEO = 3.7 V) integrated in a dual gate oxide RF-CMOS process. Ring oscillator gate delays of 2.9 ps, low-noise amplifiers for 122 GHz, and LC oscillators with fundamental-mode oscillation frequencies above 200 GHz are demonstrated.

A microelectronic biosensor was subjected to in vivo exposure by implanting it in the vicinity of m. trapezii (Trapezius muscle) from cattle. The implant is intended for the continuous monitoring of glucose levels, and the study aimed at evaluating the biostability of exposed semiconductor surfaces. The sensor chip was a microelectromechanical system (MEMS) prepared using 0.25 µm complementary metal–oxide–semiconductor CMOS/BiCMOS technology. Sensing is based on the principle of affinity viscometry with a sensoric assay, which is separated by a semipermeable membrane from the tissue. Outer dimensions of the otherwise hermetically sealed biosensor system were 39 × 49 × 16 mm. The test system was implanted into cattle in a subcutaneous position without running it. After 17 months, the device was explanted and analyzed by comparing it with unexposed chips and systems. Investigations focused on the MEMS chip using SEM, TEM, and elemental analysis by EDX mapping. The sensor chip turned out to be uncorroded and no diminishing of the topmost passivation layer could be determined, which contrasts remarkably with previous results on CMOS biosensors. The negligible corrosive attack is understood to be a side effect of the semipermeable membrane separating the assay from the tissue. It is concluded that the separation has enabled a prolonged biostability of the chip, which will be of relevance for biosensor implants in general.

Epitaxial Mn-stabilized zirconia layers on yttria-stabilized ZrO 2 (YSZ) single crystals were prepared by sputtering a Mn 0.32 Zr 0.68 O 2 target. Substrates with (001), (110) and (111) orientation were used. Transmission electron microscopy cross sections showed a homogeneous thickness of the layers. Layers prepared at a substrate temperature of 600 °C grew epitaxially. X-ray diffraction showed that these layers are not exactly cubic. We found a slightly larger out-of-plane lattice parameter compared to the in-plane lattice parameter. This means the out-of-plane lattice misfit is lower than the in-plane lattice misfit, contrary to behaviour expected for epitaxially grown layers. This effect was largest for layers on YSZ(111) and small for layers on YSZ(001).

La2Zr2O7 (LZO) islands were grown on yttria-stabilized ZrO2 (YSZ) (110) single crystals by reaction between La2O3-vapour and the heated YSZ single crystal. The samples were investigated by AFM, XRD and TEM. The pole figure of the LZO(440) plane shows that LZO islands on YSZ(110) are slightly tilted around [11¯0] with maxima at tilt angles of ±0.6° and by ±0.9° around [001]. We explain this behaviour by interfacial dislocations with a Burgers vector component perpendicular to the interface, which causes the tilt, and a component parallel to the interface which accommodates the LZO/YSZ lattice misfit of +5%. The shape of the LZO islands can be explained by the assumption that {111} planes are energetically preferred. © 2008 Elsevier B.V. All rights reserved.

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.

Integration of functional oxides on Si substrates could open a pathway to integrate diverse devices on Si-based technology. Oxygen vacancies (Vo(··)) can strongly affect solid state properties of oxides, including the room temperature ferromagnetism (RTFM) in diluted magnetic oxides. Here, we report a systematical study on the RTFM of oxygen vacancy engineered (by Pr(3+) doping) CeO2 epitaxial thin films on Si substrates. High quality, mixed single crystalline Ce1-xPrxO2-δ (x = 0-1) solid solution films were obtained. The Ce ions in CeO2 with a fluorite structure show a Ce(4+)-dominant valence state in all films. The local crystal structures of the films were analyzed in detail. Pr doping creates both Vo(··) and PrO8-complex defects in CeO2 and their relative concentrations vary with the Pr-doping level. The RTFM properties of the films reveal a strong dependence on the relative Vo(··) concentration. The RTFM in the films initially increases with higher Pr-doping levels due to the increase of the F(+) center (Vo(··) with one occupied electron) concentration and completely disappears when x > 0.2, where the magnetic polaron concentration is considered to decline below the percolation threshold, thus long-range FM order can no longer be established. We thus demonstrate the possibility to directly grow RTFM Pr-doped CeO2 films on Si substrates, which can be an interesting candidate for potential magneto-optic or spintronic device applications.

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.