Room temperature oxidation of Cu3Ge and Cu3(Si1−xGex) on Si1−xGex

Room temperature oxidation of Cu₃(Si_1−xGe_x) and Cu₃Ge films grown on Si_1−xGe_x at a temperature of 200–400°C was studied using transmission electron microscopy (TEM) in conjunction with energy dispersive spectrometry (EDS). For Cu₃(Si_1−xGe_x) and Cu₃Ge films grown at 200°C and then exposed to air, room temperature oxidation occurred. The Cu₃Ge film was superior to the Cu₃(Si_1−xGe_x) film in reducing the oxidation rate because of its higher Ge concentration. Annealing at higher temperatures such as 400°C resulted in Ge segregation out of the Cu₃(Si_1−xGe_x) film or Si diffusion from the Si_1−xGe_x substrate into the Cu₃Ge overlayer, and hence enhanced the oxidation rate of Cu₃(Si_1−xGe_x) and Cu₃Ge films. The present study shows that upon exposure to air even the Cu₃Ge film grown on Si_1−xGe_x is subject to room-temperature oxidation, revealing that the use of Cu₃Ge contacts on Si_1−xGe_x may be limited by some strict conditions.     

Growth and fundamentals of bulk β-Ga_2O_3 single crystals

The rapid development of bulk β-Ga_2O_3 crystals has attracted much attention to their use as ultra-wide bandgap materials for next-generation power devices owing to its large bandgap(～ 4.9 eV) and large breakdown electric field of about8 MV/cm. Low cost and high quality of large β-Ga_2O_3 single-crystal substrates can be attained by melting growth techniques widely used in the industry. In this paper, we first present an overview of the properties of β-Ga_2O_3 crystals in bulk form. We then describe the various methods for producing bulk β-Ga_2O_3 crystals and their applications. Finally, we will present a future perspective of the research in the area in the area of single crystal growth.     

应变Si1—xGex层材料和Si／Si1—xGex器件物理参数模型

Ｓｉ／Ｓｉ１－ｘＧｅｘ异质结系统已成功地应用于高速数字、高频微波和光电器件中。对这些器件进行理解和分析时，往往受到应变Ｓｉ１－ｘＧｅｘ材料参数缺乏的制约。本文建立和给出了常温和低温下重要应变Ｓｉ１－ｘＧｅｘ层材料和Ｓｉ／Ｓｉ１－ｘＧｅｘ器件物理参数模型，对Ｓｉ／Ｓｉ１－ｘＧｅｘ异质结器件的理解、研究和设计有重要的实际意义。     

Photoluminescence Properties of Si1—xGex／Si Strained Layer Structures

The investigation on optical properties of Si1-xGex/Si strained layer structures has been carried out actively in recent years.The photoluminescence has be-come a brisker subject in the studies of its various optical properties.A research develop-ment to photoluminescence properties of some new Si1-xGex/Si strained layer struc-tures is introduced.     

Electrical properties of Pb1 − x Mn x Te single crystals with an excess of tellurium

The effect of excess Te atoms (as high as 0.5 at %) and thermal treatment at 473 K for 120 h on the electrical conductivity σ, the thermopower coefficient α, and the Hall coefficient R of Pb_0.96Mn_0.04Te single crystals in the temperature range ～77–300 K is investigated. It is shown that excess atoms of tellurium predominantly act as acceptor impurity centers at low concentrations in unannealed samples and form antisite defects at relatively high concentrations (0.05 at % or higher) being located mainly in vacancies of the lead sublattice, and decrease the hole concentration. As a result of annealing, certain lattice defects (for example, deformational) are healed, and the accommodation process for Te atoms at lead-sublattice vacancies is intensified. These processes substantially affect the values of the electrical parameters, their temperature dependences, as well as the sign of the thermopower and Hall coefficients of the samples.     

Si／Si1—xGex异质结器件

本文综述了国外Si/Si_(1-x)Ge_xHBT的发展状况,把出Si_(1-x)Ge_xHBT的特点和优越性,分析了Si_(1-x)Ge_xHBT的制造技术和设备要求,指出了Si/Si_(1-x)Gex器件的应用前景。     

Gas source molecular beam epitaxy grown strained-Si films on step-graded relaxed Si1−xGex for MOS applications

Gas source molecular beam epitaxy has been employed for the growth of a high quality strained-Si layer on a completely relaxed step-graded Si_1−xGe_x buffer layer. As-grown strained-Si layers have been characterized using secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, and spectroscopic ellipsometry for the determination of composition, thickness, crystalline quality, and surface roughness. Heterojunction conduction and valence band offsets (ΔE_c, ΔE_υ) of strained-Si/SiGe heterostructure have been determined from measured threshold voltages of a strained-Si channel p-metal oxide semiconductor field effect transistor (MOSFET) fabricated using grown films. MOS capacitance-voltage profiling has been employed for the extraction of strained-Si layer thickness and apparent doping profile in the device.     

Optimization of PP− junction termination for new power devices

In this paper PP⁻-type junction termination is investigated. Based on 2D simulations, we have optimized this termination in the 1200–1400 V range under non-punch-through (NPT) and in the 400–600 V range under punch-through (PT) conditions. We have analysed the influence of the doping and the length of the lowly-doped P⁻ region on the efficiency of the termination and the influence of charges in the field oxide. These simulation results were then validated using test devices.     

Monolayer-precision fabrication of mixed-organic–inorganic nanohybrid superlattices for flexible electronic devices

We report a low-temperature fabrication of mixed-organic–inorganic nanohybrid superlattices for high-k thin stable gate dielectrics on flexible substrates. The self-assembled organic layers (SAOLs) were grown by repeated sequential adsorptions of CC-terminated alkylsilane and metal (Al or Ti) hydroxyl with ozone activation, which was called “molecular layer deposition (MLD)”. The MLD method is a self-controlled layer-by-layer growth process under vacuum conditions, and is perfectly compatible with the atomic layer deposition (ALD) method. The TiO₂ and Al₂O₃ inorganic layers were grown by ALD, which relies on sequential saturated surface reactions resulting in the formation of a monolayer in each sequence and is a potentially powerful method for preparing high quality multicomponent superlattices. The MLD method combined with ALD (MLD–ALD) was applied to fabricate SAOLs-Al₂O₃–SAOLs-TiO₂ nanohybrid superlattices on polycarbonate substrates with accurate control of film thickness, large-scale uniformity, excellent conformality, good reproducibility, multilayer processing capability, sharp interfaces, and excellent film qualities at relatively low temperature. The prepared ultrathin nanohybrid films exhibited good thermal and mechanical stability, good flexibility, excellent insulating properties, and relatively high dielectric constant k (6–11). The MLD–ALD method is an ideal fabrication technique for various flexible electronic devices.     

Si1 − x Ge x /Si heterostructures grown by molecular-beam epitaxy on silicon-on-sapphire substrates

The growth of heterostructures with Si_{1 ? x} Ge _x layers on $\left( {1\bar 102} \right)$ sapphire substrates by molecular-beam epitaxy with a silicon sublimation source and a germanium gas source (GeH₄) is reported. The systematic study of the influence of substrate temperature and thickness of the silicon buffer layer shows that the optimal conditions for growing epitaxial Si_{1 ? x} Ge _x layers are provided at a temperature of T _S = 375–400°C. There are significant differences in the orientations of Si_{1 ? x} Ge _x layers, depending on the thickness d of the Si buffer layer: the preferred orientations are (100) at d ≥ 100 nm and (110) for thinner layers. Heterostructures with thick (～1 μm) Si_{1 ? x} Ge _x layers, doped with erbium atoms, exhibit intense photoluminescence at λ = 1.54 μm.     

Calculation of the electron mobility for the Δ1 model of the conduction band of germanium single crystals

The concentration dependences of the charge-carrier mobility are obtained for the Δ₁ model of the conduction band of n-Ge crystals on the basis of anisotropic scattering at 77 K. It is shown that the absolute-minimum inversion of the L ₁-Δ₁ type caused by single-axis pressure on n-Ge crystals along the [100] crystallographic direction substantially decreases the charge-carrier mobility. This is explained by a decrease in the relaxation time because the effective electron masses differ only slightly in terms of different minima. For the other two cases of inversion of the L ₁-Δ₁ absolute minimum under hydrostatic and single-axis pressure along the [110] crystallographic direction, a decrease in the electron mobility is caused mainly by an increase in the effective mass. It is shown also that it is the degree of effective-mass anisotropy that substantially affects the efficiency of charge-carrier scattering in anisotropic semiconductors in this case.     

Si1—xGex合金半导体及其应用

Ｓｉ１－ｘＧｅｘ合金及其与Ｓｉ构成的应变层异质结构，量子阱、超晶格是近年来迅速发展起来的一种具有广阔应用前景的半导体微结构材料，本文着重综述了Ｓｉ１－ｘＧｅｘ合金的结构，电学，光学性质及其广阔和应用价值。     

Si／Si1—xGex／Si异质结双极晶体管中基区杂质外扩散与未掺杂Si1—xGex结隔离层

研究了Si/Si1-xGex/Si n-p-n异质结双极晶体管（HBT）的结界面处基区杂质外扩散与标定的未掺杂Si1-xGex隔离层的影响，发现，来自重掺杂基区或非突变界面处少量硼的外扩散会在导带中形成寄生势垒，它严重地影响了HBT中集电极电流的提高，未掺杂界面隔离层能消防这些寄生势垒从而极大地提高了集电极电流。     

Effect of annealing on the electrical properties of Pb1 − x Mn x Te single crystals with excess tellurium

The electrical conductivity σ, Hall coefficients R, and thermopower α of Pb_0.96Mn_0.04Te (Te) single crystals annealed at 573 K for 120 h are investigated. It is shown that, in contrast to unannealed samples, the investigated samples exhibit n-type conductivity and metal-type dependences σ(T) in the temperature range 77–300 K. It is suggested that, upon annealing, a portion of the excess tellurium atoms occupy vacancies in the lead sublattice with the formation of new vacancies in the tellurium sublattice of the samples.     

DC photoconductivity study of semi-insulating Cd1−xZnxTe crystals

Room temperature direct current (DC) photocurrents were measured for detector grade Cd_1−xZn_xTe (CZT) crystals in the spectral range of 400–1000 nm as a function of light intensity and voltage. The photocurrent data were analyzed and fit to a theoretical model to extract the electrical transport properties for high-resistivity detector grade CZT material. Using the DC photocurrent measurements, the mobility-lifetime () products and the surface recombination velocities for both electrons and holes were measured. For this study the CZT detectors had Au contacts, and the surfaces were treated in a standard 5% bromine in methanol etching solution. The correlation of the DC photocurrent measurements and detector performance is also reported.     

Mechanical and electronic properties of Ca1−xMgxO alloys

The structural, mechanical, elastics anisotropy and electronic properties of Ca_1−xMg_xO in the cubic structure are investigated using density functional theory calculations. The lattice parameters, elastic constants and elastic modulus are in excellent agreement with the experimental and others theoretical data. The sound velocities and the Debye temperatures are calculated for all the Ca_1−xMg_xO alloys using the calculated elastic constants and elastic modulus. The elastic anisotropy are characterized by calculating several different anisotropic indexes and describing the three dimensional surface constructions. Finally, electronic structure studies show that Ca_1−xMg_xO alloys are direct band gap semiconductors.     

Si1—xGex／Si Y—分支波长信号分离器

利用Ｓｉ１－ｘ的等离子体色散效应，对１．３μｍ和１．５５μｍ光通信波长的Ｓｉ基Ｓｉ１－ｘＧｅｘ波长信号分离器进行了理论分析，设计了结构参数和电学参数，并分析了其分支特性。