用电诱导液相外延法制备铝组分稳定的高铝值镓铝砷外延层

本文对用于制造高效率半导体发光器件的材料－Ｇａ１－ｘＡｌｘＡｓ（ｘ＝０．７５）外延层沿生长方向上铝组分的分布进行了详细讨论。采用电液相外延法能获得铝组分高度稳定的Ｇａ１－ｘＡｌｘＡｓ外延层，并用电流诱导效应作了初步理论解释。     

Al_xGa_（1－x）As外延层中Si平面掺杂的SIMS研究

利用二次离子质谱（ＳＩＭＳ）系统地研究了生长温度，Ａｌ组份ｘ值和Ａｓ＿４压强对Ｓｉδ掺杂Ａｌ＿ｘＧａ＿（１－ｘ）Ａｓ的ＳＩＭＳ深度剖面，Ｓｉ原子表面分凝和向衬底扩散的影响。实验发现，在外延生长Ｓｉδ掺杂Ａｌ＿ｘＧａ＿（１－ｘ）Ａｓ时，随着生长温度的提高或Ａｌ组份Ｘ值增加，Ｓｉ掺杂分布ＳＩＭＳ峰都非对称展宽，表面分凝作用加强，但不影响Ｓｉ原子的扩散，因此ＳＩＭＳ剖面的展宽与扩散无关。另外，我们还发现Ａｓ＿４压强高于１．５×１０￣（－５）ｍｂａｒ时，Ａｓ＿４压强对δ掺杂空间分布影响不大，而Ａｓ＿４压强低于此压强时，Ｓｉ掺杂分布峰宽度增加很快，这主要由杂质扩散作用引起。生长温度对掺杂分布峰影响最大，其次是Ａｌ组份影响，而较小Ａｓ＿４压强的影响不可忽视。这些研究结果对外延生长Ｓｉδ掺杂Ａｌ＿ｘＧａ＿（１－ｘ）Ａｓ材料是有价值的。     

δ－掺杂GaAs／AlxGa_（1－x）As二维电子气结构材料的GSMBE生长与特性

本文用ＧＳＭＢＥ技术生长纯度ＧａＡｓ和δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ结构二维电子气材料并对其电学性能进行了研究。对于纯度ＧａＡｓ的ＧＳＭＢＥ生长和研究，在低掺Ｓｉ时，载流子浓度为２×１０~（１４）ｃｍ~（－３），７７Ｋ时的迁移率可达８４，０００ｃｍ~２／Ｖ．ｓ。对于用ＧＳＭＢＥ技术生长的δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料，在优化了材料结构和生长工艺后，得到了液氮温度和６Ｋ迁移率分别为１７３，５８３ｃｍ~２／Ｖ．５和７．６７×１０~５ｃｍ~２／Ｖ．ｓ的高质量ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料。     

AlxGa1—xAs外延层中Si平面掺杂的SIMS研究

利用二次离子质谱系统地研究了生长温度，Ａｌ组分Ｘ值和Ａｓ４夺强对Ｓｉδ掺杂ＡｌｘＧａ１－ｘＡｓ的ＳＩＭＳ深度剖面，Ｓｉ原子表面分凝和向衬底扩散的影响。实验发现，在外延生长Ｓｉδ掺杂ＡｌｘＧａ１－ｘＡｓ时，随着生长温度的提高或Ａｌ组份Ｘ值增加，Ｓｉ掺杂分布ＳＩＭＳ峰都非对称展宽，表面分凝作用加强，但不影响Ｓｉ原子的扩散，因此ＳＩＭＳ剖面的展宽与扩散无关。     

Ga－Al－As－Si系统中Si的两性掺杂行为的研究

对Ｓｉ在电液相外延Ｇａ－Ａｌ－Ａｓ－Ｓｉ系统中的两性掺杂行为进行了研究。提出了一种恒温生长Ｇａ＿（１－ｘ）Ａｌ＿ｘＡｓ：Ｓｉｐ－ｎ结的新方法，对这种ｐ－ｎ结的成因作了定性的解释，并对这种ｐ－ｎ结的电特性加以观察。     

MOCVD外延生长Ga_(1-x)Al_xAs_(1-y)Sb_y半导体薄膜气固平衡和人工神经网络预报

本文研究了ＭＯＣＶＤ外延生长Ｇａ１－ｘＡｌｘＡｓ１－ｙＳｂｙ半导体薄膜的生长条件与外延层组成的关系，并用人工神经网络法总结有关气固平衡规律。结果表明，用气相组成，载气流量和生长温度等影响外延层组成的主要参数作为人工神经网络的输入，以固相Ｇａ１－ｘＡｌｘＡｓ１－ｙＳｂｙ中的Ａｌ和Ｓｂ的含量ｘ、ｙ作为输出，训练的人工神经网络可以预报固相组成ｘ、ｙ，得到满意结果。     

MOCVD外延生长Ga1—xAlAs1—ySby半导体薄膜气固平衡和人工神经网络预报

本文研究了ＭＯＣＶＤ外延生长Ｇａ１－ｘＡｌｘＡｓ１－６Ｓｂｙ半导体薄膜的生长条件与外延层组成的关系，并用人工神经网络法总结有关气固平衡规律。结果表明，用气相组成，载气流量和生长等影响外延层组成的主要参数作为人工神经网络的输入，以固相Ｇａ１－ｘＡｌｘＡｓ１－ｙＳｂｙ中的Ａｌ和Ｓｂ的含量ｘ、ｙ作为输出，训练的人工神经网络可以预报固相组成ｘ、ｙ，得到满意结果。     

迁移增强外延GaAs／Al／GaAs材料生长及其俄歇分析

在配有液Ｎ２冷却Ａｓ快门的分子束外延设备中利用迁殉增强外延（ＭＥＥ）方法于低温下生长了ＧａＡｓ／Ａｌ／ＧａＡｓ结构材料。俄歇测量结果表明：用ＭＥＥ方法生长 材料中Ａｌ和ＧａＡｓ之间的互扩散大大减小，在５００℃热处理后也没有引起多大的互扩散。我们还发现在高指数ＧａＡｓ（１１３）Ｂ面上用ＭＥＥ方法生长ＧａＡｓ薄膜效果更好。     

碳掺杂GaAs的MBE生长

本文在国内首次采用自行设计的碳纤维束源炉及固态源ＭＢＥ技术生长了优质碳掺杂ＧａＡｓ、ＡｌＧａＡｓ及δ碳掺杂ＧａＡｓ外延层。获得了空穴浓度从４×１０１４ｃｍ－３到２×１０１９ｃｍ－３的ＧａＡｓ材料。用霍尔效应测量仪、电化学ＣＶ剖面仪和Ｘ射线双晶衍射仪分析了外延层的质量。用Ｎｏｍａｒｓｋｉ干涉显微镜和原子力显微镜分析了ＧａＡｓ的生长过程。结果表明碳是ＧａＡｓＩＩＶ族化合物半导体的极好的ｐ型掺杂剂。     

异质外延错向角的X射线精确测量方法

通过分析外延层与衬底之间存在错向角时的衍射圆锥，利用简明的衍射几何关系提出了一个测量外延层在衬底之间错向角的方法及相应的计算错向角的公式，同时提出了检验办法，设计了一个有两外延层的ＩｎＧａＡｓ／ＩｎＡｌＡｓ／ＩｎＰ样品，用高精度ｘ射线四晶衍射仪，对样品进行了衍射测量，并应用提出的方法精确地测出两个外延层各自与衬底之间的错向角以及两个外延层之间的错向角，所得结果和理论预期值完全一致，本文也指出，采用     

高真空化学气相外延炉的研制

研制出满足Ｓｉ１－ｘＧｅｘ异质结薄膜材料生长工艺的高真空化学气相外延炉,介绍了Ｓｉ１－ｘＧｅｘ异质结薄膜材料的生长工艺,详述了该气相外延设备的性能指标、结构组成和设计原理,并且给出了利用该设备生长Ｓｉ１－ｘＧｅｘ异质薄膜的实验结果。     

Atomically controlled processing in silicon-based CVD epitaxial growth

One of the main requirements for Si-based ultrasmall device is atomic-order control of process technology. Here, we show the concept of atomically controlled processing for group IV semiconductors based on atomic-order surface reaction control in Si-based CVD epitaxial growth. Self-limiting formation of 1-3 atomic layers of group IV or related atoms after thermal adsorption and reaction of hydride gases on Si(1-x)Gex(100) (x = 0-1) surface are generalized based on the Langmuir-type model. Moreover, Si-based epitaxial growth on N, P or C atomic layer formed on Si(1-x)Gex(100) surface is achieved at temperatures below 500 degrees C. N atoms of about 4 x 10(14) cm(-2) are buried in the Si epitaxial layer within about 1 nm thick region. In the Si(0.5)Ge(0.5) epitaxial layer, N atoms of about 6 x 10(14) cm(-2) are confined within about 1.5 nm thick region. The confined N atoms in Si(1-x)Gex preferentially form Si-N bonds. For unstrained Si cap layer grown on top of the P atomic layer formed on Si(1-x)Gex(100) with P atomic amount of below about 4 x 10(14) cm(-2) using Si2H6 instead of SiH4, the incorporated P atoms are almost confined within 1 nm around the heterointerface. It is found that tensile-strain in the Si cap layer growth enhances P surface segregation and reduces the incorporated P atomic amount around the heterointerface. Heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the nm-order thick Si(1-x)Gex/Si heterointerface. These results open the way to atomically controlled technology for ULSIs.     

Characteristics of MgxZn1-xO thin film bulk acoustic wave devices

Piezoelectric thin film zinc oxide (ZnO) and its ternary alloy magnesium zinc oxide (Mg/sub x/Zn/sub 1-x/O) have broad applications in transducers, resonators, and filters. In this work, we present a new bulk acoustic wave (BAW) structure consisting of Al/Mg/sub x/Zn/sub 1-x/O/n/sup +/-ZnO/r-sapphire, where Al and n/sup +/ type ZnO serve as the top and bottom electrode, respectively. The epitaxial Mg/sub x/Zn/sub 1-x/O films have the same epitaxial relationships with the substrate as ZnO on r-Al/sub 2/O/sub 3/, resulting in the c-axis of the Mg/sub x/Zn/sub 1-x/O being in the growth plane. This relationship promotes shear bulk wave propagation that affords sensing in liquid phase media without the dampening effects found in longitudinal wave mode BAW devices. The BAW velocity and electromechanical coupling coefficient of Mg/sub x/Zn/sub 1-x/O can be tailored by varying the Mg composition, which provides an alternative and complementary method to adjust the BAW characteristics by changing the piezoelectric film thickness. This provides flexibility to design the operating frequencies of thin film bulk acoustic wave devices. Frequency responses of devices with two acoustic wave modes propagating in the specified structure are analyzed using a transmission line model. Measured results show good agreement with simulation.     

One-step Ge/Si epitaxial growth

Fabricating a low-cost virtual germanium (Ge) template by epitaxial growth of Ge films on silicon wafer with a Ge(x)Si(1-x) (0 < x < 1) graded buffer layer was demonstrated through a facile chemical vapor deposition method in one step by decomposing a hazardousless GeO(2) powder under hydrogen atmosphere without ultra-high vacuum condition and then depositing in a low-temperature region. X-ray diffraction analysis shows that the Ge film with an epitaxial relationship is along the in-plane direction of Si. The successful growth of epitaxial Ge films on Si substrate demonstrates the feasibility of integrating various functional devices on the Ge/Si substrates.     

Aluminum oxide formation at Al/La(1-x)Sr(x)MnO3 interface: a computational study for resistance random access memory applications

Resistance random access memory (ReRAM) is emerging as a next-generation nonvolatile memory. One of the most promising materials for the ReRAM application is a composite of a reactive metal [such as aluminum (Al)] and a mixed-valance manganite [such as La(1-x)Ca(x)MnO3 (LCMO) and La(1-x)Sr(x)MnO3 (LSMO)]. One of the current hypotheses regarding the origin of the resistive switching of such systems is a voltage-controlled reversible formation of a high-resistance aluminum oxide (AlO(x)) layer at the Al/LC(S)MO interface through oxygen migration from LC(S)MO. To validate this hypothesis, quantum mechanics (density functional theory) calculations were carried out on an atomistic model of the resistive-switching phenomena at the Al/LSMO interface (the composite systems of Al/LSMO and AlO(x)/LSMO) as well as on the component materials such as Al, AlO(x), LaMnO3, LaMnO(3-delta), La(1-x)Sr(x)MnO3, and La(1-x)Sr(x)MnO(3-delta). The changes in the structure, energy, and electronic structure of these systems during the oxygen vacancy formation in LSMO, the oxygen migration through the Al/LSMO interface, and the AlO(x) formation were investigated.     

Transport Properties of the Tunnel Junctions Al1-xCox/{Al1-xCox-oxide}/Al

The oxides of Al1-xCox (x=0,0.25,0.5,0.75, and 1.0) alloys were chosen as barrier materials in this work. The tunnel junction consists of the bottom electrode Al1-xCox and the top electrode Al with an insulating layer { Al1-xCox-oxide} which was formed by natural oxidation in a baking-box at 333K. The oxidation time for forming an Al1-xCox-oxide layer on the surface of the bottom Al1-xCox layers were optimized.The resistance of Al1-xCox/{ Al1-xCox-oxide}/Al tunnel junctions varied between 101 and 106 Ω measured at 1 my and 4.2 K. The effective barrier height and width of insulating layers Al1-xCox-oxide ( x=0.25, 0.5, and 0.75 )varied between 0.6 and 2.7 eV and between 1.3 and 2.1 nm. It is shown that the thin oxide layer of Al1-xCox alloys can be chosen as barrier materials.     

In(x)Ga(₁-x)As nanowires on silicon: one-dimensional heterogeneous epitaxy, bandgap engineering, and photovoltaics

We report on the one-dimensional (1D) heteroepitaxial growth of In(x)Ga(1-x)As (x = 0.2-1) nanowires (NWs) on silicon (Si) substrates over almost the entire composition range using metalorganic chemical vapor deposition (MOCVD) without catalysts or masks. The epitaxial growth takes place spontaneously producing uniform, nontapered, high aspect ratio NW arrays with a density exceeding 1 × 10(8)/cm(2). NW diameter (～30-250 nm) is inversely proportional to the lattice mismatch between In(x)Ga(1-x)As and Si (～4-11%), and can be further tuned by MOCVD growth condition. Remarkably, no dislocations have been found in all composition In(x)Ga(1-x)As NWs, even though massive stacking faults and twin planes are present. Indium rich NWs show more zinc-blende and Ga-rich NWs exhibit dominantly wurtzite polytype, as confirmed by scanning transmission electron microscopy (STEM) and photoluminescence spectra. Solar cells fabricated using an n-type In(0.3)Ga(0.7)As NW array on a p-type Si(111) substrate with a ～ 2.2% area coverage, operates at an open circuit voltage, V(oc), and a short circuit current density, J(sc), of 0.37 V and 12.9 mA/cm(2), respectively. This work represents the first systematic report on direct 1D heteroepitaxy of ternary In(x)Ga(1-x)As NWs on silicon substrate in a wide composition/bandgap range that can be used for wafer-scale monolithic heterogeneous integration for high performance photovoltaics.     

Self-assembled Al(x)Ga(1-x)N nanorods grown on Si(001) substrates by using plasma-assisted molecular beam epitaxy

Hexagonal Al(x)Ga(1-x)N nanorods were grown by plasma-assisted molecular beam epitaxy (PAMBE) on Si(001) substrates. The Al mole fraction was determined from x-ray diffraction (XRD) measurement and its value was varied from 0 to 15. It is found that, under group III-rich conditions, the growth rate of the Al(x)Ga(1-x)N nanorods decreases and the diameter increases due to the possibility of incorporation of aluminium and gallium. In order to study structural and optical properties, x-ray diffraction and cathodoluminescence (CL) measurements were carried out. The Al content (x) is calculated from these measurements and their values are compared.     

Zn(1-x)Mg(x)Te nanowires grown by solid source molecular beam epitaxy

This paper reports on the epitaxial growth of single-crystalline ternary Zn(1-x)Mg(x)Te nanowires covering a broad compositional range of molar fraction 0≤x≤0.75. The nanowires were grown on (100), (110), and (111) GaAs substrates using a vapor-liquid-solid mechanism. Solid source molecular beam epitaxy and an Au-based nanocatalyst were used for these purposes. The composition of nanowires can be adjusted by changing the ratio of Mg to Zn molecular beam fluxes. Electron microscopy images show that the nanowires are smooth and slightly tapered. The diameters of the obtained nanowires are from?30 to 70?nm and their length is around 1?μm. X-ray diffraction analysis and transmission electron microscopy reveal that the nanowires have a zinc-blende structure throughout the whole range of obtained compositions, and have a [Formula: see text] growth axis. The Raman measurements reveal both the expected splitting and shift of phonon lines with increasing Mg content, thus proving the substitutional incorporation of Mg into metallic sites of the ZnTe lattice.