LPMOCVD法生长InP、GaInAs和GaInAsP

法国汤姆逊—CSF公司的中心研究实验室已经使用低压金属有机化学气相淀积生长长波长光电子器件用高质量InP和有关化合物外延层。LPMOCVD是生长这类外延层的主要工艺。由于技术上的问题,通过液相外延难以获得大面积膜,而材料含有诸如磷之类的易挥发元素时,采用分子束外延淀积也困难。     

GaAs－InP复合材料的外延生长方法及金属半导体场效应晶体管器件制备

提出了一种新的生长过渡层的方法，并利用低压金属有机气相外延技术在ＩｎＰ衬底上生长出高质量ＧａＡｓ外延材料，用Ｘ射线双晶衍射测得５μｍ厚ＧａＡｓ外延层的（００４）晶面衍射半峰高宽（ＦＷＨＭ）低至１４０ａｒｃｓｅｃ。并制出ＧａＡｓ金属半导体场效应晶体管（ＭＥＳＦＥＴ），其单位跨导为１００ｍｓ／ｍｍ，可满足与长波长光学器件进行单片集成的需要。     

GaAs—InP复合材料的外延生长方法及金属半导体场效应晶体管器件制备

提出了一种新的生长过渡层的方法，并利用低压金属有机气相外延技术在ＩｎＰ初底上生长出高质量ＧａＡｓ外延材料，用Ｘ射线双晶衍射测得５μｍ厚ＧａＡｓ外延层的晶面衍射半峰高宽（ＦＷＨＭ）低至１４０ａｒｃ ｓｅｃ。并制出ＧａＡｓ金属半导体场效应晶体管（ＭＥＳＦＥＴ），其单位跨导为１００ｍｇ／ｍｍ，可满足与长波长光这器件进行单片集成的需要。     

硅衬底InGaN多量子阱材料生长及LED研制

利用低压金属有机化学气相沉积(MOCVD)系统在Si(111)衬底上生长了InGaN多量子阱IED外延片。为克服GaN与Si衬底之间巨大的晶格失配与热失配，引入了AIN低温缓冲层及富镓的GaN高温缓冲层，在Si(111)衬底上获得了无龟裂的InGaN多量子阱LED外延材料。在两英寸外延片内LED管芯的工作电压在3．7～4．1V之间，电致发光波长在465～480nm之间，87％的LED管芯的反向漏电流不大于0．1μA，输出光强为18～30mcd。     

光加热低压金属有机化学气相淀积生长AlGaN

采用光加热低压金属有机化学气相淀积方法成功地制备出高质量的,组分均匀的AlGaN外延层,结果表明,铝和镓的并入效率基本相等,这有别于其他研究报道,此外,建立了铝相对镓的并入效率与气相预反应之间的关系模型,它表明,光加热对预反应有较大的影响,结合GaN的生长可以看出,光加热有利于抑制预反应,从而有利于提高样品质量和铝组分的均匀性。     

半导体超薄层微结构的外延生长技术

半导体超薄层外延是超晶格与量子阱研究的技术基础。化学束外延、原子层外延、迁移增强外延、选择区域外延、激光辅助外延和低温Si外延等是在分子束外延和金属有机化学气相沉积基础上发展起来的几种新型超薄层外延技术。本文着重介绍了这些外延工艺的生长机理及其研究进展。     

半导体超薄层微结构的外延生长技术

半导体超薄层外延是超晶格与量子阱研究的技术基础。化学束外延、原子层外延、迁移增强外延、选择区域外延、激光辅助外延和低温Ｓｉ外延等是在分子束外延和金属有机化学气相沉积基础上发展起来的几种新型超薄外延技术。本文着重介绍了这些外延工艺的生长机理及其研究进展。     

Ge纳米点/Si纳米线复合结构制备及微结构特征分析

结合金属纳米颗粒辅助化学刻蚀法制备Si纳米线和低压化学气相外延自组织生长Ge纳米点制备了Ge纳米点/Si纳米线复合结构,采用电子显微镜、微区原子力/拉曼联合测试系统进行了微结构表征。Ge纳米点基本均匀地分布于Si纳米线上,通过改变生长参数可有效控制Ge纳米点的尺寸和密度。在非常扁薄的无支撑的纳米点/线复合结构中,由于应力和热效应的作用使Si和Ge的拉曼散射特征峰发生了较大的红移。     

磷化铟纳米材料制备方法的最新研究进展

详细介绍了InP纳米材料各种制备方法的特点和原理,主要包括金属有机化学气相沉积(MOCVD)、分子束外延(MBE)、化学束外延(CBE)、化学气相沉积(CVD)、热蒸发法、脉冲激光沉积(PLD)、溶剂热法、溶液-液相-固相法(SLS)、胶体化学法等,并通过比较各种制备方法的优缺点以及分析所得产物的特征概述了InP纳米材料制备技术的最新研究进展。     

MOCVD工艺中使用的特种气体

一、引言 金属有机化学气相淀积法(简称MOCVD法)是1968年由H.M.Manasevit等首先提出的。该法以挥发性金属有机物和气态的非金属氢化物作为源材料，采用与硅外延淀积相类似的生长装置，进行化合物半导体的外延淀积。     

HRXRD研究退火时间对Mg掺杂p型GaN薄膜应变状态的影响

采用低压金属有机化学气相外延(LP-MOCVD)法生长Mg掺杂p型GaN薄膜,利用高分辨X射线衍射(HRXRD)技术研究不同退火时间对GaN薄膜中外延应变的影响.研究发现应变状态随退火时间变化而发生改变.退火前水平方向为压应变.在小于最佳退火时间(15min)的时间范围内进行退火时,由于受杂质Mg在退火过程中热扩散、替位行为引起的晶格畸变以及受主中心与价带之间的电子跃迁引起的电子效应等多种因素的影响,水平应变状态由压应变向张应变转变且随时间增加应变逐渐增强.退火时间增至30min时,由于N空位增多和复合体MgGs-VN的形成以及热应力等因素的多重影响,应变状态转变为压应变.     

Effects of LP-MOCVD prepared TiO2 thin films on the in vitro behavior of gingival fibroblasts

We report on the in vitro response of human gingival fibroblasts (HGF-1 cell line) to various thin films of titanium dioxide (TiO₂) deposited on titanium (Ti) substrates by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The aim was to study the influence of film structural parameters on the cell behavior comparatively with a native-oxide covered titanium specimen, this objective being topical and interesting for materials applications in implantology. HGF-1 cells were cultured on three LP-MOCVD prepared thin films of TiO₂ differentiated by their thickness, roughness, transversal morphology, allotropic composition and wettability, and on a native-oxide covered Ti substrate. Besides traditional tests of cell viability and morphology, the biocompatibility of these materials was evaluated by fibronectin immunostaining, assessment of cell proliferation status and the zymographic evaluation of gelatinolytic activities specific to matrix metalloproteinases secreted by cells grown in contact with studied specimens. The analyzed surfaces proved to influence fibronectin fibril assembly, cell proliferation and capacity to degrade extracellular matrix without considerably affecting cell viability and morphology. The MOCVD of TiO₂ proved effective in positively modifying titanium surface for medical applications. Surface properties playing a crucial role for cell behavior were the wettability and, secondarily, the roughness, HGF-1 cells preferring a moderately rough and wettable TiO₂ coating.     

Formation of secondary iron-sulphur phases during the growth of polycrystalline iron pyrite (FeS2) thin films by MOCVD

Thin films of iron pyrite (FeS₂) have been prepared on glass and glassy carbon substrates by low pressure metal organic chemical vapour deposition (LP-MOCVD) using iron pentacarbonyl (Fe(CO)₅) and di-tert.-butyldisulphide (TBDS) as precursors. The TBDS partial pressure was varied from 1 to 100 Pa for different iron pentacarbonyl partial pressures (0.25, 0.5 and 1 Pa) while all other parameters were maintained constant. It was found that there is a critical TBDS-partial pressure of about 30 Pa for a deposition temperature of 475 °C, where a drastic change in the layer properties occurs. Below this TBDS partial pressure pyrrhotite type phases (Fe_1-xS) will be formed although there is a sulphur precursor excess in the gas phase. If the layers contain pyrrhotite, the electrical properties of the FeS_x-films are changed significantly. The occurrence of the pyrrhotite phases does not depend on the growth rate, hence it is not controlled kinetically. Therefore, the sulphur pressure above the growing pyrite film is the important parameter controlling the solid phase. The present investigation shows that, in order to prepare pyrite thin films of good electronic quality, one has to take care to avoid the secondary sulphur-iron phases even in very small concentrations.     

薄膜太阳电池用TCO薄膜制造技术及其特性研究

阐述了玻璃衬底、柔性衬底透明导电氧化物薄膜(Transparent conductive oxides-TCO)以及硅基薄膜太阳电池应用方面的最新研究成果。绒面结构可以提高薄膜太阳电池效率和稳定性并降低生产成本。磁控溅射技术和LP-MOCVD技术是制造绒面结构ZnO-TCO薄膜(例如"弹坑"状和"类金字塔"状表面)的主流生长技术;高迁移率TCO薄膜(IMO、IWO、ZnO∶Ga等)以及柔性衬底TCO薄膜是研究开发的重点。     

The growth of thin films of copper chalcogenide films by MOCVD and AACVD using novel single-molecule precursors

Highly oriented crystalline films of copper sulfide and copper selenide have been grown on glass by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) and by aerosol-assisted chemical vapor deposition (AACVD), using the novel air-stable compounds Cu(E₂CNMeⁿHex)₂]* (where E=S,Se). Thin films of non-stoichiometric cubic CuS and CuSe have been deposited in the temperature range 450–500 °C.     

Interrupted Mg doping of GaN with MOCVD for improved p-type layers

Uniformity doping, δ-doping and growth-interruption doping to produce gallium nitride (GaN): Mg has been investigated by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). It was demonstrated by electrical, optical, and surface studies that films produced by growth-interruption-Mg-doping produce the best crystal quality, this doping method increasing self-compensation because of the incorporation of additional impurities during the interruption period. Mg-δ-doping employs GaN:Mg/UGaN superlattices valence band edge oscillation to enhance hole concentration leading to significantly reduced p-type resistivity, enhanced hole mobility. This doping method also leads to improved surface morphology.     

GaN buffer layer growth by MOCVD using a thermodynamic non-equilibrium model

In this work, a gallium nitride (GaN) buffer layer was grown on a sapphire substrate (α-Al₂O₃) in a horizontal reactor by low pressure metal-organic chemical vapor deposition (LP-MOCVD). Trimethylgallium (TMGa) and ammonia (NH₃) were precursors of gallium and nitrogen, respectively, and hydrogen (H₂) was used as carrier gas. TMGa and NH₃ fluxes were kept constant, with flow rates of 3.36 μmole/min and 0.05 standard liter/min, respectively. The fluence of hydrogen was also kept constant with the flux rate of 4.5 standard liter/min. GaN was deposited at 550 °C and 100 mbar. According to the X-ray diffraction spectra, a buffer layer was formed with a wurtzite structure, which is the stable phase. The thermodynamic affinities were estimated as A₁ = 175.9 kJ/mole and A₂ = 62.88 kJ/mole.     

The LP-MOCVD of CdS/Bi2S3 bilayers using single-molecule precursors

The single-molecule precursors [Cd(S₂CNMe n-Hex)₂] and [Bi(S₂CNMe n-Hex)₃] (Me=methyl; n-Hex=n-hexyl) were used to prepare CdS/Bi₂S₃ layers by low-pressure metal organic chemical vapour deposition (LP-MOCVD). The bilayers were deposited onto glass substrates at 400–450 °C for varying growth conditions. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical measurements. The results were compared with those obtained for the single phases.     

Characterization of GaN epitaxial layers on SiC substrates with AlxGa1−xN buffer layers

High quality GaN epitaxial layers were obtained with Al_xGa_1−xN buffer layers on 6H–SiC substrates. The low-pressure metalorganic chemical vapor deposition (LP-MOCVD) method was used. The 500 Å thick buffer layers of Al_xGa_1−xN (0≤x≤1) were deposited on SiC substrates at 1025°C. The FWHM of GaN (0004) X-ray curves are 2–3 arcmin, which vary with the Al content in Al_xGa_1−xN buffer layers. An optimum Al content is found to be 0.18. The best GaN epitaxial film has the mobility and carrier concentration about 564 cm² V⁻¹ s⁻¹ and 1.6×10¹⁷ cm⁻³ at 300 K. The splitting diffraction angle between GaN and Al_xGa_1−xN were also analyzed from X-ray diffraction curves.     

Homogenous indium distribution in InGaN/GaN laser active structure grown by LP-MOCVD on bulk GaN crystal revealed by transmission electron microscopy and x-ray diffraction

We present transmission electron microscopy (TEM) and x-ray quantitative studies of the indium distribution in In(x)Ga(1-x)N/GaN multiple quantum wells (MQWs) with x = 0.1 and 0.18. The quantum wells were grown by low-pressure metalorganic chemical vapour deposition (LP-MOCVD) on a bulk, dislocation-free, mono-crystalline GaN substrate. By using the quantitative TEM methodology the absolute indium concentration was determined from the 0002 lattice fringe images by the strain measurement coupled with finite element (FE) simulations of surface relaxation of the TEM sample. In the x-ray diffraction (XRD) investigation, a new simulation program was applied to monitor the indium content and lateral composition gradients. We found a very high quality of the multiple quantum wells with lateral indium fluctuations no higher than Δx(L) = 0.025. The individual wells have very similar indium concentration and widths over the whole multiple quantum well (MQW) stack. We also show that the formation of 'false clusters' is not a limiting factor in indium distribution measurements. We interpreted the 'false clusters' as small In-rich islands formed on a sample surface during electron-beam exposure.