GexSi1-x合金中的键长及其对电子能带结构的影响

采用经验紧束缚理论，以类似闪锌矿结构的晶体模型模拟Ge_xSi_1-x合金，根据总能最小原则计算了Ge_xSi_1-x合金中的键长及点阵常数．同时以紧束缚方法计算了原子位置发生弛豫前后的电子能带结构，并与虚晶近似下的计算结果进行了比较．计算结果表明，Ge_xSi_1-x合金中的键长基本上与合金组分无关，各自接近于Ｇｅ，Ｓｉ晶体中的键长，与广延ｘ射线吸收精细结构（ＥＸＡＦＳ）测量结果符合得 关键词：     

Surfactant-mediated growth of Si1-xSnx layers by molecular-beam epitaxy

1-x Sn_x (0.01≤x≤0.04) layers on Si(001) and relaxed Si-Ge substrates. The Si_1-xSn_x layers were investigated using Rutherford backscattering spectrometry, atomic force microscopy, transmission electron microscopy and preferential-etching experiments. The investigation of surfactant-mediated growth of epitaxial Si_1-xSn_x was motivated by a possible use of relatively higher growth temperatures without relaxation by surface precipitation. It is demonstrated that higher growth temperatures are attainable when Bi is used as surfactant if the surface-segregated Sn layer is relatively small, equivalent to Si_1-xSn_x layers of low strain. The increase in growth temperature leads to a significant improvement in the crystalline quality of these Si_1-xSn_x layers. Received: 4 December 1998/Accepted: 9 December 1998     

Raman scattering in Ge-Ge1-xSix superlattice

Raman studies of Ge based Ge_1-xSi_x superlattices are presented. Using Raman spectroscopy as a local probe, only the first Ge-Ge_1-xSi_x bilayer underneath the surface is explored. It is shown that the top Ge layer experiences a biaxial elastic stress which we evaluate. The silicon content of the Ge_1-xSi_x layer is deduced from the peak frequency of both Ge-Ge and Ge-Si bond vibrations. The Ge-Ge_1-xSi_x interfacial perfection is also investigated. The Raman data reveal a smearing of this heteroboundary.     

Dopant diffusion and segregation in semiconductor heterostructures: Part 2. B in GexSi1-x/Si structures

x Si_1-x/Si heterostructures have been obtained. Here the chemical effects seem to be of less importance. The Fermi-level effect determines the ionized boron solubilities in Ge_xSi_1-x and in Si, as well as the thermal equilibrium concentration of the singly-positively-charged crystal self-interstitials I⁺ which governs the boron diffusion process. The junction carrier concentration affects the concentration of I⁺ and solubility of B in the region and hence controls B diffusion across the heterojunction. Received: 20 August 1998/Accepted: 23 September 1998     

高完整GexSi1-x/Si应变超晶格的X射线双晶衍射研究

本文用X射线双晶衍射技术对分子束外延生长的Ge_xSi_1-x/Si应变超晶格的结构参数进行研究,分别采用X射线运动学理论和动力学理论对超晶格的双晶摆动曲线进行计算模拟,得出超晶格的全部结构参数;并对这两种理论计算模拟的结果进行比较,发现这两种理论计算的结果基本一致,只是在细微结构上略有差别,对高完整Ge_xSi_1-x/Si超晶格,用动力学理论计算的曲线更接近于实验曲线。 关键词：     

An effective compliant substrate for low-dislocation relaxed Si1-xGex growth

An effective compliant substrate for Si_1-xGe_x growth is presented. A silicon-on-insulator substrate was implanted with B and O forming 20 wt % borosilicate glass within the SiO₂. The addition of the borosilicate glass to the buried oxide acted to reduce the viscosity at the growth temperature of Si_1-xGe_x, promoting the in situ elastic deformation of the thin Si (∼20 nm) layer on the insulator. The sharing of the misfit between the Si and the Si_1-xGe_x layers was observed and quantified by double-axis X-ray diffraction. In addition, the material quality was assessed using cross-sectional transmission electron microscopy, photoluminescence and etch pit density measurements. No misfit dislocations were observed in the partially relaxed 150-nm Si_0.75Ge_0.25 sample as-grown on a 20% borosilicate glass substrate. The threading dislocation density was estimated at 2×10⁴ cm^-2 for 500-nm Si_0.75Ge_0.25 grown on the 20% borosilicate glass substrate. This method may be used to prepare compliant substrates for the growth of low-dislocation relaxed SiGe layers. Received: 4 January 2001 / Accepted: 30 May 2001 / Published online: 17 October 2001     

Si离子注入对分子束外延Si1-xGex/Si量子阱发光特性的影响

对分子束外延生长带边激子发光的Si_1-xGe_x/Si量子阱结构，通过Si离子自注入和不同温度退火，观测到深能级发光带和带边激子发光的转变.Si离子注入量子阱中并在600℃的低温退火，形成链状或小板式的团簇缺陷，它导致深能级发光带的形成，在850℃的高温退火后重新观测到带边激子发光.这种团簇缺陷的热离化能约为0.1eV，比Si中空穴或填隙原子缺陷的热激活能(约0.05eV)高.这表明早期文献中报道的深能级发光带是由类似的团簇缺陷产生的. 关键词：     

用于电压基准的Nb/NbxSi1-x/Nb约瑟夫森单结的研制

现代可编程约瑟夫森电压基准的核心器件是约瑟夫森结阵.目前最具有优势的约瑟夫森结阵是 Nb/Nb_xSi_1-x/Nb材料的结阵. Nb/Nb_xSi_1-x/Nb材料的约瑟夫森结 具有三层薄膜的制作过程简便, Nb和Nb_xSi_1-x刻蚀工艺相同以及Nb_xSi_1-x 势垒层成分可调等优点.中国计量科学研究院设计制作了Nb/Nb_xSi_1-x/Nb约瑟夫森单结. 通过在4.2 K低温下对所做单结进行直流电流-电压特性测量,观测到了清晰的超导隧穿电流和 从零电压态向电压态的跳变,最后就测量结果进行了分析讨论.此项工作属于国内首个开展 Nb/Nb_xSi_1-x/Nb材料约瑟夫森单结研究的工作.     

First-principles calculations of the effect of Ge content on the electronic,mechanical and acoustic properties of Li17Si4-xGex

The electronic, mechanical and acoustic properties of Li₁₇Si_4-xGe_x (x = 0, 2.3, 3.08, 3.53, and 4) have been investigated by using first-principles calculations based on the density functional theory (DFT). The research shows that the bulk modulus B, Young's modulus E, shear modulus G, and hardness H_v gradually decrease with the increasing Ge content. Li₁₇Si_4-xGe_x have the brittle nature from the analysis of B/G ratio and Cauchy pressure. The maximum Young's moduli are all along [1 1 0] plane, and the sequence of degree of anisotropic property is Li₁₇Ge₄ > Li₁₇Si_0.48Ge_3.52 > Li₁₇Si_0.92Ge_3.08 > Li₁₇Si_1.7Ge_2.3 > Li₁₇Si₄. The analysis of acoustic velocity shows that all the sound velocities decrease with the increasing Ge content for Li₁₇Si_4-xGe_x (x = 0, 2.3, 3.08, 3.53, and 4), and the longitudinal wave along [111] direction is fastest for the studied compounds. Debye temperature Θ_D, v_t and v_l decrease with the increasing Ge content. The minimum thermal conductivity decreases with the increasing Ge content, and Li₁₇Si_4-xGe_x have low thermal conductivities and are not potential thermal conductors. The analysis of electronic properties indicates that Li₁₇Si_4-xGe_x have the metal nature and anisotropic electrical conductivity. The electric conduction is improved with the increasing Ge content.     

高能电子衍射研究H钝化偏角Si衬底上Si,GexSi1-x的分子束外延生长模式

用高能电子衍射(RHEED)研究H钝化偏角Si衬底上Si,Ge_xSi_1-x材料的分子束外延(MBE)生长模式,发现经低温处理的H钝化Si衬底上要经过10nm左右的Si生长才能获得比较平整的表面.Si,Ge_xSi_1-x外延时的稳定表面均以双原子台阶为主,双原子台阶与单原子台阶并存的结构.Si双原子台阶上的Si二聚体列(dimerrow)取向垂直于台阶边缘,而Ge_xSi_1-x双原 关键词：     

Strain-balanced Si<Subscript>1-x</Subscript>Ge<Subscript>x</Subscript>/Si type II quantum wells for 1.55 μm detection and emission

This work deals with the optoelectronic properties of heterostructures built on type II Si_1-xGe_x/Si strained quantum wells grown on relaxed Si_1-yGe_y/Si (001) pseudo-substrates. To limit the intrinsic problem due to the real-space indirect nature of the interface, we propose and model three heterostructures having three different potential profiles of the valence and conduction bands which consist in various arrangements of Si and Si_1-xGe_x barriers of different Ge contents. The proposed stacks are designed in a pragmatic way for a pseudomorphic growth on relaxed Si_1-yGe_y assuming individual layer thickness being smaller than the known critical thickness and an overall compensation of the strain. Variation of thickness and compositions (x>y) permits to optimize i) the quantum confinement of electrons and heavy-hole levels and ii) the wave function's overlap and the out-of-plane oscillator strength. The optimum parameters satisfy a fundamental emission at a key 1.55 μm wavelength below the absorption edge of each layer constitutive of the stacks. A comparison between the characteristics of the three heterostructures brings out the superior advantages of the W architecture.     

GexSi1-x/Si应变层超晶格的分子束外延生长及其特性研究

在Si(100)衬底上用分子束外延在不同的温度下生长了不同组份的Ge_xSi_1-x/Si应变层超晶格。用反射式高能电子衍射、X射线双晶衍射、卢瑟福背散射、透射电子显微镜以及Raman。散射等测试方法研究了Ge_xSi_1-x/Si超晶格的生长及其结构特性。结果表明,对不同合金组份的超晶格,其最佳生长温度不同。x值小,生长温度高;反之,则要求生长温度低。对于x为0.1—0.6,在400—600℃的生长温度范围能够长成界面平整、 关键词：     

生长在GexSi1-x(001)衬底上应变GaAs层的价电子能带结构与光学性质

采用紧束缚方法对生长在Ge_xSi_1-x(001)衬底上的应变ＧａＡｓ层的价电子能带结构和空穴的三次非线性光学极化率x⁽³⁾进行了计算结果表明，由于应变的存在，使ＧａＡｓ层的空穴有效质量和价带态密度变小，而使偏振方向在（００１）面内的三次非线性光学极化率x_xxxx⁽³⁾变大． 关键词：     

A method for the experimental determination of the net atomic charge via X-ray photoemission spectroscopy

A method for the experimental determination of the net charge distribution over the atoms in a large class of compounds is described. The method is based on X-ray photoemission spectroscopy and requires the determination of two core-level energies per constituting atomic species. Two special cases of large conceptual and practical interest are discussed: the silicon charge in CoSi₂, Si_1-xGe_x (0≤x≤0.3), SiC, Si₃N₄ and SiO₂, and the aluminum charge in aluminum-doped zeolites. Received: 20 March 2000 / Accepted: 28 March 2000 / Published online: 21 March 2001     

外延Si1-xGex薄层中浅杂质的光热电离光谱

在Si_1-xGe_x合金外延层中利用光热电离光谱方法观察到了Si_0.92Ge_0.08合金中浅施主磷的2p_±及3p_±态的分立谱线，并根据有效质量近似理论估算了Si_0.92Ge_0.08合金中磷施主的电离能为45.51meV．与硅相比，由于合金的无序效应，Si_1-xGe_x合金的分立谱线发生明显展宽 关键词：     

用深能级瞬态谱方法研究赝晶Si/Ge0.25Si0.75/Si单量子阱的价带偏移

应变的Ge_xSi_1-x层和未应变的硅层间的能带偏移主要是价带偏移。量子阱中载流子的热发射能与界面的能带偏移有着密切的关系。本文用深能级瞬态谱(DLTS)研究分子束外延生长的p型Si/Ge_0.25Si_0.75/Si单量子阱的价带偏移,阱宽为15nm,考虑到电场的影响和量子阱中第一子能级的位置,对从DLTS得到的热发射能进行适当的修正,可以计算出Si/Ge_0.25Si_0.75/S 关键词：     

Oxidation process of SiGe on SOI substrates

The oxidation of SiGe film epitaxial grown on top of SOI wafers has been studied. These SiGe/SOI samples were oxidized at 700, 900, 1100 °C. Germanium atoms were rejected from SiGe film to SOI layer. A new Si_1−xGe_x (x is minimal) layer formed at SiGe/Si interface. As the germanium atoms diffused, the new Si_1−xGe_x (x is minimal) layer moved to Si/SiO₂ interface. Propagation of threading dislocation in SiGe film to SOI substrate was hindered by the new SiGe/Si interface. Strain in SOI substrate transferred from SiGe film was released through dislocation nucleation and propagation inner. The relaxation of SiGe film could be described as: strain relaxed through strain equalization and transfer process between SiGe film and SOI substrates. Raman spectroscopy was used to characterize the strain of SiGe film. Microstructure of SiGe/SOI was observed by transmission electron microscope (TEM).     

p型GexSi1-x/Si多量子阱的红外吸收及其分析

通过测量GeSi多量子阱的红外谱，同时观察到了相应于量子阱内重空穴基态HH1到重空穴激发态HH1、轻空穴激发态LH1和自旋分裂带SO及连续态间的跃迁吸收．测量了GeSi多量子阱探测器的正入射光电流谱，看到了明显的光响应峰．理论计算中计及了轻、重和自旋分裂带间的耦合及能带的非抛物性，并自洽考虑了哈特里势和交换相关势．与实验结果比较，认为带之间的耦合，使子带间的跃迁情况变得复杂，是正入射吸收产生的原因 关键词：     

Impurity distribution and electrical characteristics of boron-doped Si1−x Ge x /Si p +/N heterojunction diodes produced using pulsed UV-laser-induced epitaxy and Gas-immersion laser doping

A two-step pulsed UV-laser process which independently controls the metallurgical and electrical junction depth of a Si_1–x Ge _x /Si heterojunction diode has been implemented. Pulsed Laser-Induced Epitaxy (PLIE) combined with Gas-immersion Laser Doping (GILD) are used to fabricate boron-doped heteroepitaxial p ⁺/N Si_1–x Ge _x /Si layers and diodes. Borontrifluoride is used as the gaseous dopant source in the GILD process step. Boron incorporation and activation are investigated as a function of laser energy fluence and the number of laser pulses using SIMS and Halleffect measurements. The dose of incorporated dopant is on the order of 10¹³ cm^–2 per pulse. The B profiles obtained are flat except for a peak at the interface resulting from segregation effects. The B and Ge distributions are compared with shifts in the turn-on voltage of p ⁺/N Si_1–x /Si heterojunction diodes produced by the process. The GILD/PLIE process is spatially selective with the resulting diodes fabricated being quasiplanar. Hole mobilities in the heavily doped Si_1–x Ge _x films are found to be slightly lower than in comparable Si films.Presently at the Oregon Graduate Institute, Beaverton, OR 97006, USA     

The mobility of electrons in strained silicon

The development of Si and Si_1−xGe_x layer growth by molecular beam epitaxy has enabled heterostructures and HEMT devices to be made with Group IV semiconductors. Strain is very important in determining the electronic behaviour of this system and as an initial step towards understanding mobility in SiGe HEMT structures a Monte Carlo technique has been used to simulate electron transport in bulk Si, strained by commensurate growth on a (001) Si_1−yGe_y buffer. The in-plane mobility initially increases with increasing strain but then falls at higher strains and fields. Results are presented for both undoped and 10¹⁷ cm⁻³ n-type Si, fields of 10² to 10⁴ Vcm⁻¹ and strain levels up to the equivalence of growth on a Si_0.25Ge_0.75 buffer. The results are explained by the splitting of the degenerate conduction band minimum and the transition probability between the two-fold and four-fold split minima.