射频等离子体发射光谱分析在分子束外延GaN生长中的应用

研究了射频等离子体辅助分子束外延生长GaN晶膜中氮等离子体的发射光谱。用非接触式测量方法-光谱法测定了等离子体特性。讨论了分子束外延生长系统参数的变化与等离子体发光光谱变化之间的联系，薄膜生长与等离子体内活性粒子之间的关系。     

射频等离子体发射光谱分析在分子束外延GaN生长中的应用

研究了射频等离子体辅助分子束外延生长GaN晶膜中氮等离子体的发射光谱。用非接触式测量方法———光谱法测定了等离子体特性。讨论了分子束外延生长系统参数的变化与等离子体发光光谱变化之间的联系 ,薄膜生长与等离子体内活性粒子之间的关系     

新型分子束外延束源快门的研制

束源快门在分子束外延技术中占有重要地位,是分子束外延设备上的关键部件之一。针对国产MBE—Ⅰ、Ⅱ型手动快门的种种不足,设计了一种新型的磁力偶合电脉冲驱动快门。其结构简单、小巧、紧凑,运转灵活、可靠。理论上开关时间为0.04秒。采用防污染措施。可有效地防止砷对快门的污染。新型快门的出现将有助于高质量分子束外延生长以及自动化生长过程的实现,并可应用于新一代分子束外延设备上。     

分子束外延生长GaAs中δ掺杂研究

利用二次离子质谱（ＳＩＭＳ）和电化学剖面Ｃ－Ｖ方法研究了生长温度对ＧａＡｓ中理想Ｓｉδ掺杂的结构的偏离和掺杂原子电微活效率的影响。实验发现，外延生长Ｓｉδ掺杂，ＧａＡｓ时，随着生长温度的升高，Ｓｉ掺杂分布ＳＩＭＳ峰非对称展宽。表面分凝作用加强，但不影响Ｓｉ原子扩散。另外，Ｓｉ施主电激活效率随着生长温度的提高而增大。     

进一步提高我国分子束外延技术的探讨

进一步提高我国分子束外延技术的探讨孔梅影，梁基本，曾一平（中国科学院半导体研究所北京１０００８３）十多年来，我国的分子束外延（ＭＢＥ）技术从无到有，并不断改进提高，取得很大的进展。在中国科学院一些单位的共同努力下，我国先后发展了Ⅰ、Ⅱ、Ⅲ、Ⅳ四种型号...     

Si局域分子束外延技术

利用局域分子束外延技术生长了含有ＳｉＧｅ量子阱的岛状结构２，实现了生长的岛状结构 面不与掩模材料相接触。这种含有量子际的岛状结构具有比相同结构量子阱强２０多倍的光致发光强度。     

HgCdTe分子束外延柔性制造技术研究

报道了近年来在ＨｇＣｄＴｅ分子束外延柔性制造技术研究中取得的初步结果,并对面临的任务进行了讨论。研究表明：ＨｇＣｄＴｅ分子束外延薄膜具有很好的组分均匀性、表面形貌、电学参数以及组分可重复性。用分子束外延ＨｇＣｄＴｅ薄膜成功地研制出了３２×３２红外焦平面器件。     

射频分子束外延生长氮化铝材料中缺陷的研究

采用射频分子束外延方法生长了氮化铝薄膜材料,研究了生长条件对外延层中位错和点缺陷等晶体缺陷的影响.结果表明,在富Al条件下,适当提高生长温度有利于抑制位错的产生,但同时会引入更多的氧杂质点缺陷.而对于空位点缺陷,在富Al条件下进行二维生长可同时增强Al和N原子的迁移,因此可有效地减少Al空位和N空位.但是,相比于Al空位,薄膜中的N空位更难以消除.     

分子束外延的计算机控制

报导了一种专门为MBE生长而设计的计算机控制系统，改善并扩展了原控制单元SentinelⅢ的功能，并展示了由它控制生长的各种SiGe结构。     

激光分子束外延

介绍了激光分子束外延(Laser Molecular Beam Epitaxy)的基本原理和技术特点,评述了激光分子束外延技术在超导材料和磁性材料方面所取得的主要成就,并给出了这种技术在材料科学领域的应用前景和发展潜力.     

缓冲层对氮化镓二维生长的影响

报道了在射频等离子体（RF-Plasma)辅助的分子束外延（MBE）技术中，使用白宝石（0001）衬底，采用低温缓冲层工艺外延氮化镓（GaN)。通过原子力显微镜（AFM）的表面形貌比较及X射线双晶衍射（XRD）ω扫描摇摆曲线的分析，讨论了低温缓冲层成核机理及缓冲层生长温度与形成准二维生长的关系，确立了缓冲层的三维成核，准二维生长的生长机理，并在此基础上实现了氮化镓外延层更好地二维生长，进一步提高了氮化镓外延层的晶体质量。     

GaN材料的GSMBE生长

在国内首次用ＮＨ３作氮源的ＧＳＭＢＥ方法在α－Ａｌ２Ｏ３衬底上生长出了ＧａＮ单昌外延膜。ＧａＮ生长速率可达０．５μｍ／ｈ。ＧａＮ外延膜的（０００２）双晶Ｘ射线衍射峰回摆曲线的半高宽最窄为８ａｒｃｍｉｎ。霍尔迁移率为５０ｃｍ＾２／Ｖ．ｓ。对质量好的ＧａＮ膜，室温阴性发光谱上只有一个强而锐的近岸边发光峰，谱峰位于３７２ｎｍ处，谱峰半高宽为１４ｎｍ（１２５ｍｅＶ）。     

RF Plasma MBE生长GaN材料及特性研究

用ＲＦＰｌａｓｍａ ＭＢＥ方法生长出了ＧａＮ 材料,它的Ｘ 射线衍射半峰宽为３３５ 秒,７７Ｋ 下ＰＬ发光峰半峰宽为２２ｍｅＶ,表明了材料具有较高的晶体质量。根据Ｘ射线衍射分析,位错密度约为７ ．３ ×１０８ｃｍ －２ 。用Ｓｉ 作为掺杂剂,所得载流子浓度可覆盖１０１７ － １０１９ｃｍ －３ 的范围。掺Ｓｉ ＧａＮ 的ＰＬ谱表明,Ｓｉ 的引入可提高材料的发光效率。     

常温下采用射频等离子体法合成碳化硅膜

采用射频等离子体增强的气相沉积法，以硅烷和乙烯为原料，在常温下成功的合成了碳化硅薄膜。对于该条件下合成的碳化硅薄膜的结构特征，采用SEM、TEM、XRD、IR等手段进行了分析；分析结果表明我们的样品是以碳硅键为主的薄膜。     

Effect of nitridation on crystallinity of GaN grown on GaAs by MBE

GaN films are grown on [0 0 1] GaAs substrates by plasma-assisted molecular beam epitaxy using a three-step process that consists of a substrate nitridation, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. Films are evaluated by X-ray diffraction and the dependence of crystalline quality on the nitridation temperature is studied. It is demonstrated that nitridation has to be performed at low-temperature to achieve c-oriented α-GaN. Higher nitridation temperature promotes formation of mis-oriented domains and β-GaN inclusions     

Plasma-assisted molecular beam epitaxy of ZnO on in-situ grown GaN/4H-SiC buffer layers

Plasma-assisted molecular beam epitaxy (MBE) was used to grow ZnO(0001) layers on GaN(0001)/4H-SiC buffer layers deposited in the same growth chamber equipped with both N- and O-plasma sources. The GaN buffer layers were grown immediately before initiating the growth of ZnO. Using a substrate temperature of 440°C–445°C and an O₂ flow rate of 2.0–2.5 sccm, we obtained ZnO layers with smooth surfaces having a root-mean-square roughness of 0.3 nm and a peak-to-valley distance of 3 nm shown by AFM. The FWHM for X-ray rocking curves recorded across the ZnO(0002) and ZnO(101ˉ5) reflections were 200 and 950 arcsec, respectively. These values showed that the mosaicity (tilt and twist) of the ZnO film was comparable to corresponding values of the underlying GaN buffer. It was found that a substrate temperature >450°C and a high Zn-flux always resulted in a rough ZnO surface morphology. Reciprocal space maps showed that the in-plane relaxation of the GaN and ZnO layers was 82.3% and 73.0%, respectively and the relaxation occurred abruptly during the growth. Room-temperature Hall-effect measurements showed that the layers were intrinsically n-type with an electron concentration of 10¹⁹ cm^–3 and a Hall mobility of 50 cm²·V^–1·s^–1.     

Growth condition dependence of unintentional oxygen incorporation in epitaxial GaN

Growth conditions have a tremendous impact on the unintentional background impurity concentration in gallium nitride (GaN) synthesized by molecular beam epitaxy and its resulting chemical and physical properties. In particular for oxygen identified as the dominant background impurity we demonstrate that under optimized growth stoichiometry the growth temperature is the key parameter to control its incorporation and that an increase by 55?°C leads to an oxygen reduction by one order of magnitude. Quantitatively this reduction and the resulting optical and electrical properties are analyzed by secondary ion mass spectroscopy, photoluminescence, capacitance versus voltage measurements, low temperature magneto-transport and parasitic current paths in lateral transistor test structures based on two-dimensional electron gases. At a growth temperature of 665?°C the residual charge carrier concentration is decreased to below 10¹⁵ cm^?3, resulting in insulating behavior and thus making the material suitable for beyond state-of-the-art device applications.     

Fabrication and characterisation of p-type GaN metal-semiconductor-metal ultraviolet photoconductors grown by MBE

We have fabricated interdigital metal-semiconductor-metal ultraviolet photoconductors using p-type GaN grown by MBE. The material had a hole concentration of 10¹⁸ cm⁻³ and a mobility of 5 cm² V⁻¹ s⁻¹. The spectral response of the detectors has been measured and it shows a peak at 364.2 nm (3.402 eV) possibly caused by excitonic effects. The transient response of the photodetector cannot be described by a single time constant. The rise and fall times of the photoresponse are different indicating that the theory usually applied to GaN photoconductors is not valid.     

Influence of AlN buffer layer thickness and deposition methods on GaN epitaxial growth

A gallium nitride (GaN) epitaxial layer was grown by metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates with aluminum nitride (AlN) buffer layers at various thicknesses. The AlN buffer layers were deposited by two methods: radio frequency (RF) magnetron sputtering and MOCVD. The effect of the AlN deposition method and layer thickness on the morphological, structural and optical properties of the GaN layers was investigated. Field emission scanning electron microscopy showed that GaN did not coalesce on the sputtered AlN buffer layer. On the other hand, it coalesced with a single domain on the MOCVD-grown AlN buffer layer. Structural and optical analyses indicated that GaN on the MOCVD-grown AlN buffer layer had fewer defects and a better aligned lattice to the a- and c-axes than GaN on the sputtered AlN buffer layer.     

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.