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In order to suppress dislocation generation, we develop a “three-step growth” method to heteroepitaxy low dislocation density germanium (Ge) layers on silicon with the MBE process. The method is composed of 3 growth steps: low temperature (LT) seed layer, LT-HT intermediate layer as well as high temperature (HT) epilayer, successively. Threading dislocation density (TDD) of epitaxial Ge layers is measured as low as 1.4 × 10 6  cm −2 by optimizing the growth parameters. The results of Raman spectrum showed that the internal strain of heteroepitaxial Ge layers is tensile and homogeneous. During the growth of LT-HT intermediate layer, TDD reduction can be obtained by lowering the temperature ramping rate, and high rate deposition maintains smooth surface morphology in Ge epilayer. A mechanism based on thermodynamics is used to explain the TDD and surface morphological dependence on temperature ramping rate and deposition rate. Furthermore, we demonstrate that the Ge layer obtained can provide an excellent platform for III–V materials integrated on Si. [ABSTRACT FROM AUTHOR]

Thick Ge layers grown on Si(0 0 1) are handy for the production of GeOI wafers, as templates for the epitaxy of III-V and GeSn-based heterostructures and so on. Perfecting their crystalline quality would enable to fabricate suspended Ge micro-bridges with extremely high levels of tensile strain (for mid IR lasers). In this study, we have used a low temperature (400 °C)/high temperature (750 °C) approach to deposit with GeH 4 various thickness Ge layers in the 0.5 µm – 5 µm range. They were submitted afterwards to short duration thermal cycling under H 2 (in between 750 °C and 875–890 °C) to lower the Threading Dislocation Density (TDD). Some of the thickest layers were partly etched at 750 °C with gaseous HCl to recover wafer bows compatible with device processing later on. X-ray Diffraction (XRD) showed that the layers were slightly tensile-strained, with a 104.5–105.5% degree of strain relaxation irrespective of the thickness. The surface was cross-hatched, with a roughness slightly decreasing with the thickness, from 2.0 down to 0.8 nm. The TDD (from Omega scans in XRD) decreased from 8 × 10 7 cm −2 down to 10 7 cm −2 as the Ge layer thickness increased from 0.5 up to 5 µm. The lack of improvement when growing 5 µm thick layers then etching a fraction of them with HCl over same thickness layers grown in a single run was at variance with Thin Solid Films 520, 3216 (2012). Low temperature HCl defect decoration confirmed those findings, with (i) a TDD decreasing from slightly more 10 7 cm −2 down to 5 × 10 6 cm −2 as the Ge layer thickness increased from 1.3 up to 5 µm and (ii) no TDD hysteresis between growth and growth then HCl etch-back. [ABSTRACT FROM AUTHOR]

We have investigated the low temperature epitaxy of high Sn content GeSn alloys in a 200 mm industrial Reduced Pressure - Chemical Vapor Deposition tool from Applied Materials. Gaseous digermane (Ge 2 H 6 ) and liquid tin tetrachloride (SnCl 4 ) were used as the Ge and Sn precursors, respectively. The impact of temperature (in the 300–350 °C range), Ge 2 H 6 and SnCl 4 mass-flows on the GeSn growth kinetics at 100 Torr has been thoroughly explored. Be it at 300 °C or 325 °C, a linear GeSn growth rate increase together with a sub-linear Sn concentration increase occurred as the SnCl 4 mass-flow increased, irrespective of the Ge 2 H 6 mass flow (fixed or varying). The Sn atoms seemed to catalyze H desorption from the surface, resulting in higher GeSn growth rates for high SnCl 4 mass-flows (in the 4–21 nm min −1 range). The evolution of the Sn content x with the F ( SnCl 4 ) 2 · F ( Ge 2 H 6 ) mass-flow ratio was fitted by x 2 ( 1 - x ) = n · F ( SnCl 4 ) 2 · F ( Ge 2 H 6 ) , with n  = 0.25 (325 °C) and 0.60 (300 °C). We have otherwise studied the impact of temperature, in the 300–350 °C range, on the GeSn growth kinetics. The GeSn growth rate exponentially increased with the temperature, from 15 up to 32 nm min −1 . The associated activation energy was low, i.e. E a  = 10 kcal mol −1 . Meanwhile, the Sn content decreased linearly as the growth temperature increased, from 15% at 300 °C down to 6% at 350 °C. [ABSTRACT FROM AUTHOR]

This paper reviews recent considerable progress made in the last few years in understanding the behavior and properties of intrinsic point defects close to moving melt/solid Si interfaces during single crystal Si growth from a melt. The so called Voronkov criterion allows to determine whether the grown Si crystal is interstitial I - or vacancy V -rich. This criterion is written as the ratio Γ of the pulling rate v over the thermal gradient G at the interface. Crystals pulled with Γ above a critical value Γ crit are vacancy-rich while below Γ crit , they are interstitial-rich. Various expressions based on the intrinsic point defect thermal equilibrium concentration and diffusivity have been proposed to calculate Γ crit and are briefly discussed in this paper. Recently it was shown that the thermal stress at the interface and heavy doping with neutral and/or electrically active impurities, have a considerable impact on the intrinsic point defect balance and thus also on Γ crit . Furthermore, high energy barriers of formation energies of I and V around three or four atom layers from (001) free surface support a model in which the boundary conditions of the point defect concentrations at the surface in simulations can be set at fixed values. The situation is quite different for Ge single crystal pulling where the vacancy is always the dominant intrinsic point defect so that the Voronkov criterion cannot be applied. Prediction of vacancy cluster concentration/size distributions as a function of the pulling conditions is however still possible. The possibility of reaching Voronkov criterion conditions for Ge by doping with specific impurities is also discussed. Finally, impacts of stress and doping on self-diffusion in Si and Ge are evaluated with comparing the previous experimental results. [ABSTRACT FROM AUTHOR]

In this research, a computer program was written to calculate the distribution of impurities after many times of passing the melt section through the sample. This code is used to obtain necessary conditions to achieve highly pure germanium with impurity less than 1ppb. Finally, the behaviour of different impurities in zone refining process was simulated to obtain important parameters such as the number of pass through the sample for a desired purity of the material. It was found, If C 0 =E-4 and L/l=20, after 100 passes, it would be required to remove 12.25 l from the front surface and 5.35 l from the end surface of the sample to have maximum 1ppb impurity concentration in remaining germanium material. [ABSTRACT FROM AUTHOR]

A technique to locally grow germanium-on-insulator (GOI) structure on silicon (Si) platform is studied. On (001) Si wafer, silicon dioxide (SiO 2 ) is thermally grown and patterned to define growth window for germanium (Ge). Crystalline Ge is grown via selective hetero-epitaxy, using SiO 2 as growth mask. Lateral overgrowth of Ge crystal covers SiO 2 surface and neighboring Ge crystals coalesce with each other. Therefore, single crystalline Ge sitting on insulator for GOI applications is achieved. Chemical mechanical polishing (CMP) is performed to planarize the GOI surface. Transmission electron microscopy (TEM) analysis, Raman spectroscopy, and time-resolved photoluminescence (TRPL) show high quality crystalline Ge sitting on SiO 2 . Optical response from metal–semiconductor–metal (MSM) photodetector shows good optical absorption at 850 nm and 1550 nm wavelength. [ABSTRACT FROM AUTHOR]

• Strained Ge microbridges along [1 1 1] direction are fabricated based on Ge-on-Si(1 1 0). • Strong PL was obtained from the Ge microbridge the [1 1 1] uniaxial tensile-strain. • PL spectra from dry-etched Ge microbridges show Fabry-Perot resonant peaks. • We successfully regrew a strained SiGe layer on the Ge microbridge. • We observed strong emissions at shorter wavelength from the SiGe/Ge microbridge. Strained SiGe/Ge microbridges are fabricated based on Ge-on-Si(1 1 0). The Si(1 1 0) substrate is employed to fabricate the microbridge along [1 1 1] direction as uniaxial strain in the [1 1 1] direction is expected to be the most effective to shift the direct valley of the conduction band. As a result, very strong room temperature photoluminescence is obtained from the fabricated Ge microbridge. It is remarkable that Fabry-Perot resonant peaks are seen in this emission, which is attributed to the vertical side wall of the bridge realized by the anisotropic dry etching process. Moreover, for the purpose of controlling of the emission wavelength, a SiGe layer is regrown on the Ge microbridge. We observe strong emissions from the SiGe at shorter wavelength, demonstrating that the emission wavelength can be controlled using SiGe/Ge hetero structures on the microbridge and this structure is very promising for realization of efficient light sources for Si photonics. [ABSTRACT FROM AUTHOR]

• It was found the crack formation was suppressed for the SiGe on the patterned GOS. • SiGe layers on the patterned GOS was completely strained. • Crack formation was caused by propagation. Strained SiGe layers are grown on Ge(1 1 1) and Ge-on-Si(1 1 1) substrates with and without forming mesa-patterning, where the Ge and Ge-on-Si(1 1 1) outside of the defined mesa-pattern area are etched down by various thicknesses. We find that high-density cracks are formed both inside and outside of the mesa-area and the cracks are connected across the mesa-boundary when the Ge layer partially remains outside of the mesa area (partially etched case). By contrast, the crack formation is completely suppressed when the Ge is fully etched, leaving the Si on the etched surface. These results mean that the cracks are initially generated in the SiGe layer grown on the Ge outside of the mesa-area and they propagate into the mesa-area, making the mesa-area covered with crack networks. In addition, since it is implied that the density of the crack generation sources is not high, the crack-free SiGe can be grown in the mesa area by fully removing the Ge layer outside of the mesa area. Therefore, the patterning method can provide very attractive templates highly applicable to strained SiGe-based optoelectronic and spintronic devices with superior performances. [ABSTRACT FROM AUTHOR]

Abstract: Previous Raman spectroscopy studies on SiGe alloys have left rather large uncertainties concerning the relationships between the Raman peaks׳ frequency shifts and stress. In this paper, we systematically revisit these relationships, confirm some coefficient values and propose new relationships linking the Raman peak shift to stress and Ge concentration. Different types of stacks were grown and studied to that end: (1) Thick, nearly fully relaxed SiGe virtual substrates grown on Si (001), whose lattice parameter is close to that of bulk material for a given Ge composition (in-between 20% and 100%). (2) Thin, fully compressively-strained SiGe layers grown on Si (001), with a Ge content in the 5–55% range. The cross-examination with Raman spectroscopy and X-ray diffraction of those stacks provided us with precise values of the coefficients linking the Raman peak shift to (i) the Ge content of the SiGe layer (thanks to SiGe virtual substrates) and (ii) the magnitude of stress in the SiGe layer (thanks to thin, fully pseudomorphic layers). [Copyright &y& Elsevier]

This investigation demonstrates the temperature-dependent mechanical properties of Si80Ge20 alloy films via a nanoindenter in the indentation depth of 100nm. The roughly equal root mean square roughness (R rms) values and repeatable load–displacement (P–δ) curves for the samples ensure the mechanical performances mainly contributed from the influences of annealing temperatures. The hardness (H) values of samples increase with the temperatures of an initial annealing in the range from RT to 900°C, and, conversely, decrease for annealing temperatures over 900°C. Accordingly, both E/H and h f/h max values, exhibiting an inverse tendency in the above temperature range, hints that the solid solution strengthening effect and the softening phenomenon occur for the initial-annealing and over-annealing stages, respectively. In addition, grazing incidence X-ray diffraction (GIXRD) analysis demonstrates the lattice expansion and the broadened peak that attribute to the solid solution strengthening of samples and the segregation of Ge, respectively. Through observing the value of the (200) lattice spacing of 5.624Å for a 900°C-annealed sample by transmission electron microscopy (TEM) analysis, it is verified that the segregation of Ge is responsible for the decreased hardness for the 1000°C-annealed sample. [ABSTRACT FROM AUTHOR]

Abstract: An adaptive phase field model is used to study the morphological instability and the facet formation during a directional solidification of SiGe alloys. Using highly anisotropic surface free energy and cusp kinetic functions, as well as a proper temperature gradient, the simulated critical growth velocity for various alloy concentrations is in good agreement with classical theories and experimental observations. The simulated facet formation and kinetics are also consistent with the experiments as well. [Copyright &y& Elsevier]

Abstract: This paper reports on the growth and characterization of highly compressive strained GeSn layers on thin strain relaxed Ge virtual substrates on Si wafers. Sn concentration up to 12.5%, which is about more than 10 times the thermal equilibrium predicted for GeSn binaries, are successfully epitaxially grown by ultra-low temperature (160°C) molecular beam epitaxy. A minimum channeling yield of 9% evidence the high crystalline quality of the GeSn alloys while angular channeling scan demonstrate that all GeSn layers are fully pseudomorphic on the relaxed Ge virtual substrate. The strain analysis shows a deviation from the Vegard's law for Sn contents above 8%. The analysis is completed by the Raman mode dependence on the alloys composition. [Copyright &y& Elsevier]

• 550 °C epitaxy of tensile SiP. with disilane and phosphine. • Various strategies evaluated to obtain low resistivities and high [P]subst. • High phosphine to disilane mass-flow, low H2 carrier flow and high pressure. • Smooth and uniform t-Si:P layers with a substitutional P concentration of 6.3%. • Electrical resistivity much lower than with a chlorinated chemistry. Our long-term aim was to explore the Low Temperature Cyclic Deposition/Etch (CDE) of tensile-Si:P, in order to engineer the Sources and Drains of n-type Field Effect Transistors. We wanted to have high amounts of tensile strain and low resistivities in tensile Si:P layers grown at 550 °C, with (i) mainstream Si 2 H 6 + PH 3 gases for the non-selective deposition of t-Si:P and (ii) HCl + GeH 4 for the selective etches of amorphous-Si:P versus monocrystalline Si:P (to have selectivity on patterned wafers). In the current study, we have focused on the deposition in such processes, having shown beforehand that, indeed, t-Si:P could be etched at 550 °C with HCl + GeH 4 if the process conditions were right (Hartmann J.M. and Veillerot M., 2020 Semicond. Sci. Technol. 35 015015). Thanks to (i) high F(PH 3)/(2*F(Si 2 H 6)) Mass-Flow Ratios (MFR), (ii) a reduction of the H 2 carrier flow, from the reference value of a few tens of standard liters per minute down to 1/5th of it and (iii) a chamber pressure increase, from 20 Torr up to 90 Torr, we succeeded in dramatically increasing the "substitutional" P concentration. and reaching values as high as 7.9%. 40 Torr was the best pressure in order to simultaneously have (i) a high "substitutional" P concentration (6.3%), (ii) a reasonable t-Si:P growth rate (5.5 nm min−1) and (iii) a low electrical resistivity (0.41 mOhm·cm), without being hampered by a layer uniformity that would be too degraded to be of use in actual devices. Those t-Si:P layers, grown with a MFR of 0.46, were of superior crystalline quality (in X-Ray Diffraction) and smooth (from haze measurements). [ABSTRACT FROM AUTHOR]

Abstract: Melt zone growth of Ge-rich SiGe alloy was performed on 24mm diameter by >90mm long feedrods using a resistive furnace. The Si composition along the growth axis of one sample showed a trend where the composition first rapidly decreased, then smoothly transitioned into a plateau-like region, and finally dropped in a Bridgman-like manner near the end of processing. A simple one-dimensional model including full mixing of the melt constituents and an equilibrium Si segregation coefficient given by the phase diagram of SiGe was used to explain the results. The model is in good agreement with the Si composition profile along the growth axis. [Copyright &y& Elsevier]

Abstract: We report on the characterization of high Sn-content (∼10% Sn) GeSn films grown on (001) Ge/Si substrates using reduced-pressure chemical vapor deposition. Pseudomorphic 30nm GeSn films were grown on relaxed Ge buffers, exhibit a smooth surface, and display strong photoluminescence (PL) with cavity-resonance fringes from the Ge buffer. Additional luminescence studies confirm that the measured PL originates from the GeSn film. A study on the effects of rapid thermal annealing is presented along with evidence of Sn surface segregation and formation of surface nanodots for anneals at 450°C and above. Anneals at 400°C for up to 500s showed little change in PL intensity or material properties, which suggest that a critical temperature exists for post-growth thermal-processing of high Sn-content, compressively-strained GeSn films. [Copyright &y& Elsevier]

Abstract: Recently, great improvements have been obtained on Chemical Vapor Deposition (CVD) processes and their integration in advanced MOS technologies. Actually, Si and SiGe materials realized by CVD processes are excellent candidates to provide technical solutions what ensure the continuing device performance enhancement. This work reports an extensive investigation regarding the anisotropic effects observed when Si and SiGe films are grown by CVD processes on various Si surface orientations. To focus as possible, our study on intrinsic and fundamental growth parameters, simple hydride chemistry was used for the different depositions. In this case, we have first observed that the film morphology and the film thickness strongly depend on the surface orientation. Then, we have characterized the anisotropy of the growth kinetics and proposed a model explaining its origin in our experimental conditions. This model is based on surface structure and dangling bond density considerations and, for a simple deposition illustrated by the Si epitaxy this model seems to explain the root cause of faceting appearance. Finally, compared to Si material, the SiGe hetero-epitaxy is found to be more sensitive to the anisotropic effects. Therefore, we supposed in this latter case, the influence of others mechanisms, such as mixing or growth modes. [Copyright &y& Elsevier]

Abstract: Vertical Bridgman growth of GeSi alloy with an average Si composition of 15atom% was performed on a large 25mm diameter by 90mm long melt volume to significantly increase the buoyancy-driven convection within the melt. For one sample, the longitudinal Si composition along the sample length is described by a simple one-dimensional model including complete mixing of the Ge and Si melt constituents and the equilibrium Si segregation coefficient given by the GeSi phase diagram. The excellent agreement between theory and experiment shows that the GeSi phase diagram in the Ge-rich region is determined accurately. [Copyright &y& Elsevier]

Abstract: In this paper experimental results on the effect of the Ge doping on the distribution of dislocations in directional solidified multi-crystalline (mc) Si are presented. The dislocation density distribution is analyzed on the basis of the average dislocation density and the cumulative probability by means of etch pits counting via optical auto-focus (AF) microscope and the Photovoltaic (PV) scan method. The Ge doped ingots show a significantly lower average dislocation density and dislocations are more homogeneously distributed in the Si matrix, whereas the undoped ingot contains large areas of accumulated dislocations. Apparently, the overall dislocation density is reduced by the induced strain field and the lower mobility of dislocations due to the pinning effect. [Copyright &y& Elsevier]

Abstract: Bulk Germanium–Silicon single crystal alloys have been grown using a novel crystal growth technique called Axial Heat Processing (AHP). The technique includes an immersed baffle which divides melt into two regions, decreases the melt height, and distributes the heat over the entire growth interface. Two silicon doped germanium single crystals with 12 atomic percent concentration have been grown by the AHP method at 2mm/h velocity, and two single crystals with identical growth parameters have also been grown using the Vertical Bridgman technique to set a base for comparison between the crystals grown by the two techniques. The effect of the processing variables on segregation and single crystal quality is investigated. [Copyright &y& Elsevier]

Abstract: In this work, we have developed a reduced pressure chemical vapor deposition (RP-CVD) epitaxial process to grow strain-balanced Ge/Si0.4Ge0.6 multilayers on 200mm diameter Si(100) substrates, via an intermediate relaxed Si0.2Ge0.8/Ge buffer. The results obtained indicate that with proper selection of the epitaxial growth conditions, strain-balanced multilayered heterostructures can be produced with the precise Si0.4Ge0.6 alloy content and control of the strained epilayer thicknesses to within a few monolayers. XTEM analysis clearly resolved very abrupt Ge/Si0.4Ge0.6 heterointerfaces and the sample surfaces were seen, by AFM, to be very smooth with an RMS surface roughness below 1.5nm. [Copyright &y& Elsevier]

Abstract: During the last decade, the 300mm silicon wafer has been optimized and one is studying the move to 450mm crystals and wafers. The ever increasing silicon crystal diameter leads to two important trends with respect to substrate characteristics: the interstitial oxygen concentration decreases while the size of grown in voids and crystal originated particles (COPs) in vacancy-rich crystals is increasing. The first effect is due to the large melt in which movements have to be controlled and partly suppressed by the use of magnetic fields. This magnetic confinement leads to a more uniform dopant incorporation but at the same time to a more limited transport of oxygen from the quartz crucible to the melt and the growing crystal. The reduced interstitial oxygen concentration and the lower thermal budget of modern device processing leads to strongly reduced oxygen precipitation and thus internal gettering capacity. The increasing COP size (accompanied by a decreasing density) is caused by the decreasing pulling rate and thermal gradient that have to be used in order to avoid dislocation formation. The slower cooling of the crystal leads to a decreased void nucleation rate and at the same time to an increased thermal budget for void growth as well as a larger number of vacancies available per void. In the present paper the effect of germanium doping in the range between 1016 and 1019 cm−3 on COP formation and oxygen precipitation is discussed and illustrated. Also the beneficial effect of germanium doping with respect to wafer breakage during processing, with respect to the suppression of thermal donor formation and with respect to improving device radiation hardness is addressed. [Copyright &y& Elsevier]

Abstract: Single-crystal Ge1−x Sn x alloys (x=0.025, 0.052, and 0.078) with diamond cubic structure have been grown on Si(001) substrates by molecular beam epitaxy (MBE), using high-quality Ge thin films as buffer layers. The Ge1−x Sn x alloys are nearly fully strained and have high crystalline quality without Sn surface segregation, revealed by the measurements of high resolution X-ray diffraction (HRXRD), Rutherford backscattering spectra (RBS), and transmission electron microscopy (TEM). In addition, thermal stability investigations show that the alloy with Sn composition of about 2.5% can be stable at 500°C, which may enable it for device applications. [Copyright &y& Elsevier]

Abstract: A commercially available 300mm single-wafer UHV-CVD reactor was used to grow strained pseudomorphic Si0.79Ge0.21 layers beyond the critical thickness on Si substrates. A unique in situ method of introducing controlled amounts of oxygen at the growth interface, combined with a very sensitive defect etching technique, was used to study the crystal defects present in the strained SiGe layers immediately after growth and after thermal annealing over large areas (many square centimeters). The etching results showed that the density of growth-related defects (stacking faults) originating from residual O at the epitaxy/substrate interface increases exponentially when the interfacial O concentration exceeds a level of about 1013 O/cm2 as measured by secondary ion mass spectroscopy. By defect etching the annealed samples we demonstrate that all the strain-relieving defects (dislocations) we observed originate from these growth defects. Therefore, we confirm previous claims that the strain metastability of low-misfit SiGe layers is controlled mainly by the initial concentration of growth defects. These findings have important implications regarding historical studies of metastability in the strained SiGe/Si system as well as contemporary efforts to grow highly metastable strained layers for IC applications. [Copyright &y& Elsevier]

Abstract: We have studied in reduced pressure chemical vapor deposition the growth kinetics of Si and Si0.8Ge0.2 on bulk Si(001) and on silicon-on-insulator (145nm buried oxide/20nm Si over-layer) substrates. For this, we have grown at 650°C, 20Torr 19 periods (Si0.8Ge0.2 19nm/Si 32nm) superlattices on both types of substrates that we have studied in secondary ion mass spectrometry, X-ray diffraction and cross-sectional transmission electron microscopy. The Si and SiGe growth rates together with the Ge content are steady on bulk Si(001), with mean values around 9.5nmmin−1 and 20.2%, respectively. In contrast, growth rates decrease from ∼9.5nmmin−1 down to values around 7.0nmmin−1 (SiGe) and 6.3nmmin−1 (Si), when the deposited thickness on SOI increases from 0 up to slightly more than 100nm. They then go back up to values around 8.8–9.0nmmin−1 as the thickness increases from 100 up to 400nm. They then slowly decrease to values around 8.4–8.6nmmin−1 as the thickness increases from 400 up to 800nm. The Ge concentration follows on SOI exactly the opposite trend: an increase from 19.9% (0nm) up to 20.6% (∼100nm) followed by a decrease to values around 20.1% (400nm) then a slow re-increase up to 20.4% (800nm). These fluctuations are most likely due to the following SOI surface temperature variations: from 650°C down to 638°C (100nm), back up to 648°C (400nm) followed by a slow decrease to 646°C (800nm). These data curves will be most useful to grow on conventional SOI substrates large number of periods, regular Si/Si0.8Ge0.2 superlattices that will serve as the core of multi-channel or three-dimensional nano-wires field effect transistors. [Copyright &y& Elsevier]

Abstract: The growth and electronic structural studies of diluted magnetic semiconducting (DMS) materials Ge0.93Mn0.07 and Ge0.97Mn0.03 have been carried out. The melt growth technique has been used for growing these samples. Electronic structure has been studied using the maximum entropy method (MEM) using X-ray powder data sets. The covalent nature of bonding and the interaction between the atoms are clearly revealed by these studies. One-dimensional electron density profile along bonding and non-bonding directions have been plotted to understand the details of bonding very clearly. The mid-bond electron density between the atoms is 0.377e/Å3 for Ge0.93Mn0.07 and 0.455e/Å3 for Ge0.97Mn0.03. The local structure of these materials has been determined using the pair distribution function (PDF) analysis and the changes in the nearest neighbor distances are quantified and analyzed. [Copyright &y& Elsevier]

Abstract: We have prepared Ge0.92Mn0.08 thin films by molecular beam epitaxy (MBE) on semi-insulating (001) GaAs substrates and investigated their transport and magnetic properties. We have found out that the resulting properties of the thin films are highly dependent on the substrate temperature T s. The sample grown at T s=130°C exhibited a pronounced negative magnetoresistance and anomalous Hall effect even up to room temperature most probably due to the presence of substitutional Mn in the Ge host matrix and the formation of the Ge5Mn3 phase. Because these phenomena were not detected for samples grown above 130°C, we believe that these are due to the T s dependence of Mn distribution in Ge0.92Mn0.08 thin films and the degree of the interdiffusion of Ge, Ga and As atoms at the Ge0.92Mn0.08/GaAs interface. [Copyright &y& Elsevier]

Abstracts: As a strain-relief relaxed Si1− x Ge x buffer that is used for type II band offset formation, we have proposed a quadruple-Si1− x Ge x -layer (QL) buffer where misfit dislocations are evenly distributed in the lower two interfaces and a buffer surface with good crystallinity was obtained. The crystallinity of the buffer surface does not degrade by high P doping with a P concentration of ∼1019 cm−3 during the buffer growth. A vertical-type electron-tunneling Si/Si1− x Ge x resonant tunneling diode (RTD) formed with the highly P-doped QL buffer exhibits a high current density and a high peak-to-valley current ratio (PVCR) value. A planer-type electron-tunneling Si/ Si1− x Ge x RTD formed with the same buffer using tetramethyl ammonium hydroxide (TMAH) etching and polyimide insulator, which is better suited for device integration, also exhibits a high current density and a high PVCR value and good initial static performance reproducibility. [Copyright &y& Elsevier]

The aim of this study being the selective epitaxial growth of either intrinsic or in situ doped raised sources and drains, we have studied the growth kinetics and the boron and phosphorus doping of Si and SiGe with a dichlorosilane+germane+hydrochloric acid chemistry. Adding HCl to SiH2Cl2+GeH4 leads at the same time to a strong decrease of the Si or SiGe growth rate and to a significant increase in the germanium content of the layers. Switching from bulk to SOI substrates with a very thin Si top layer induces a significant decrease in the Si growth rate, which we have quantified as a function of the buried oxide thickness. As far as the doping at 800°C of Si layers grown with a SiH2Cl2+HCl chemistry is concerned, we have obtained a peak for B ions at 1.3×1020 cm−3. Beyond this peak, poly-crystalline Si:B layers are formed. Meanwhile, the phosphorus ion concentration in Si increases monotonously with the PH3 flow, reaching a maximum value equal to 1.3×1019 cm−3. Switching over to Si0.8Ge0.2 (grown at 700°C with a chlorinated chemistry) enables to drastically reduce the resistivity (minima: 9.75×10−4 Ω cm for SiGe:P and 1.02×10−3 Ω cm for SiGe:B) and thus meet, for a lower thermal budget, the requirements of the forthcoming 45 nm gate length technology node (not reached for Si:P). Finally, as far as growth kinetics are concerned, carrying out some heavy boron (phosphorus) doping induces a strong increase (decrease) of the Si or SiGe growth rate and a reduction (strong increase) of the apparent Ge concentration. [Copyright &y& Elsevier]

In this paper, the Ge overgrowth of oxidized and reduced Ge/Si islands is studied. The islands were grown in a hot-wall ultrahigh vacuum chemical vapour deposition reactor. The oxidation was performed in air at room temperature and the reduction in a hydrogen atmosphere at 600°C. After reduction, Ge was deposited at the same temperature. The results of the overgrowth show that the reduced native oxide on top of the islands transfers the epitaxial information from the Si substrate to the epitaxial layer, whereas no growth takes place outside the Ge islands. This makes it possible to use these islands as crystal seeds for epitaxial lateral overgrowth for growing Ge layers on top of Si substrates. [Copyright &y& Elsevier]

The wetting angles and surface tension of Ge1−xSix melts (0.02) have been measured on various substrate materials using the sessile drop technique. Fused quartz, sapphire, SiC, glassy carbon, pBN, AlN, and Si3N4 were used as substrates. The highest and most stable wetting angles were found for pBN substrates with 164±8°, either under forming gas with an additional carbon getter in the system or under active vacuum. The surface tension measurements resulted in a value of +2.2×10−3 N/m at% Si for the concentration dependence ∂γ/∂C. For the composition range measured, the temperature dependence ∂γ/∂T showed values similar to those of pure Ge, on average −0.07×10−3 N/m K. [Copyright &y& Elsevier]

Atomic force microscopy is used to investigate a series of arsenic-mediated growth experiments in the molecular beam epitaxy of Ge on Si(0 0 1). The experiments are performed by first depositing Ge at a coverage of 6 ML (where three-dimensional islands form), followed by additional growth of Ge with coevaporation of As. During the As-mediated second growth stage no new islands appear as expected of the surfactant effect. However, the shapes of the Ge islands formed in the first stage are observed to change from pyramids and domes to mesas that have different base orientations and flat (0 0 1) tops of significantly increased areas. Because the island facets can be viewed as stacks of atomic steps, the island shape changes suggest As-induced step movements during the Ge growth, which are important to understand the mechanisms of surfactant suppression in the formation of three-dimensional islands. [Copyright &y& Elsevier]

The effect of the supply of depleted Si solute elements on the compositional variation in the Si-rich SiGe bulk crystals was studied using the method which was used to grow Ge-rich SiGe single crystals with a uniform composition. By selecting the proper pulling rate, we can obtain Si-rich Si1−xGex bulk crystals with uniform composition of x=0.1 without using the supply mechanism of depleted Si solute elements. When the supply mechanism of Si solute elements was used, the initial composition in Si-rich SiGe crystals can be much more easily determined by controlling the growth temperature than that in Ge-rich crystals because the Si seed crystal is not melted down. The supply of Si solute elements is very effective to change the compositional variation even for Si-rich SiGe crystals. [Copyright &y& Elsevier]

Abstract: Joint experimental and theoretical study of Ge nanoislands growth on pit-patterned Si substrate is carried out. Si(001) and Si(111) substrates, that have been templated by means of electron beam lithography and reactive ion etching, were used to grow Ge by molecular-beam epitaxy. Atomic-force-microscopy studies showed that, at certain conditions of Ge growth on the Si(001) and Si(111) pit-patterned substrates, Ge nanoislands are formed at the pits'' edges and inside the pits, respectively. The effect is interpreted in terms of energy surfaces mapped out through molecular dynamics simulations of pit-patterned surface. [Copyright &y& Elsevier]

• Ultra high hole mobility Ge films were grown on Si (1 0 0) by MBE. • TDD can be greatly reduced from 109 cm−2 to 107 cm−2 by in-situ annealing treatments. • The room temperature mobility 1252 cm2/V·s is achieved. • The 90° periodic interfacial misfit arrays are achieved at the Ge/Si interface. We have demonstrated an effective method to achieve ultra high mobility in the Ge films grown directly on Si (1 0 0) using molecular beam epitaxy (MBE). The Hall effect measurements revealed that the unintentionally doped Ge films have a hole mobility up to 1252 cm2/V·s at room temperature and 3855 cm2/V·s at 80 K. A proper combination of low temperature epitaxy and high temperature post annealing provides the opportunity on defect reduction and interface modulation. The periodic 90° interfacial misfit (IMF) array formed at the Ge/Si interface is believed to contribute to a preferential strain relieve at the interface and the ultra high mobility. [ABSTRACT FROM AUTHOR]

• Reduced Pressure – Chemical Vapor Deposition of GeSi alloys at low temperatures. • Epitaxial growth at 100 Torr with digermane, dichlorosilane and/or disilane. • Lower growth rates and much higher Si contents with Si2H6 than with SiH2Cl2. • Higher precursor flows enable GeSi 7% growth at temperatures as low as 325 °C. • Variable density islands on GeSi layers grown at temperatures less than 400 °C. GeSn/GeSi multi quantum wells with (i) high Sn content, direct bandgap GeSn wells and (ii) GeSi barriers with Si contents in the few %–30% range might be of use in optoelectronics. As GeSn has to be grown in the 300–375 °C range (to avoid Sn segregation/precipitation), GeSi barriers should also be grown in that temperature range, too. GeSi might also be used to passivate, at low temperatures, the surface of Ge-rich imagers and photo-detectors. Thanks to X-Ray Reflectivity (thickness) and X-Ray Diffraction (Si content), I have therefore explored, in a 200 mm Chemical Vapour Deposition tool, the 100 Torr growth of tens of nm thick GeSi layers on Ge(0 0 1) buffers. Precursor gases were Ge 2 H 6 (Ge), SiH 2 Cl 2 and/or Si 2 H 6 (Si). Whatever the chemistry, a temperature increase in the 350–500 °C range resulted in an increase, (a stabilization) then a decrease of the GeSi growth rate. Meanwhile, the Si content increased almost linearly with the temperature. For given Si and Ge flows, GeSi growth rates were higher and Si contents lower with SiH 2 Cl 2 than with Si 2 H 6. Adding SiH 2 Cl 2 to Si 2 H 6 had, quite surprisingly, almost no impact on the GeSi growth kinetics, which was mainly governed by the Si 2 H 6 flow. With high precursor flows, I succeeded in having, with Ge 2 H 6 and SiH 2 Cl 2 , GeSi growth rates increasing from 2 up to 32 nm min−1 as the temperature increased from 325 °C up to 375 °C, with a Si content close to 7.5%. Growth rates increased from 0.6 up to 19 nm min−1 and Si contents decreased from 24 down to 22% over the same temperature range with Ge 2 H 6 , SiH 2 Cl 2 and Si 2 H 6. [ABSTRACT FROM AUTHOR]