GaN的MOVPE生长和m－i－n型蓝光LED的试制

利用自行研制的常压ＭＯＶＰＥ设备和全部国产ＭＯ源，采用低温生长缓冲层技术，在蓝宝石（α－Ａｌ２Ｏ３）衬底上获得了高质量的ＧａＮ外延层。未掺杂的ＧａＮ外延层的室温电子迁移率已达１１４ｃｍ２／Ｖ．ｓ，载流于浓度为２×１０１８。７７Ｋ光致发光谱近带边发射峰波长为３６５ｎｍ，其线宽为４ＤｍｅＶ。Ｘ射线双晶衍射回摆曲线的线宽为３６０ａｒｃｓｅｃ。用Ｚｎ掺杂生长了绝缘的ｉ－ＧａＮ层。在此基础上研制了ｍ－ｉ－ｎ型ＧａＮ的ＬＥＤ，并在室温正向偏压下发出波长为４５５ｎｍ的蓝光。     

用MOVPE技术生产明天的太阳能电力

开发高性能化合物半导体太阳电池的兴趣在不断增长。三结GaInP／Ga（h）As／Ge电池的转换效率已达到39％。许多公司正在研制与这些电池配套使用的聚光器系统。本文从研究者利用MOVPE（金属有机物气相外延）技术生长其它化合物半导体器件所积累经验的角度评述了化合物半导体电池工艺。描述了目前多结电池的一般结构及需要解决的某些问题，正在研究旨在使转换效率达到≥40％的新的器件结构，此项工艺增长潜力巨大，因为高效多结聚光器系统有可能以较大份额进入PV市场。     

1．52μmInGaAsP／InP分别限制量子阱激光器

报导了在６００℃生长温度下以三甲基镓（ＴＭＧａ）和三甲基铟（ＴＭＩｎ）为Ⅲ族源，用低压金属有机气相沉积（ＬＰ－ＭＯＣＶＤ）技术生长出的高质量１．６０μｍ和１．３μｍＩｎＧａＡｓＰ材料，以及在其分别限制量子讲结构生长的情况下，用质子轰击方法制得的条形结构量子阱激光器。该激光器在室温下直流阈值电流为１００ｍＡ。     

半导体材料研究的新进展

概述了目前半导体材料研究最有代表性的超薄层微结构材料的新进展。由于MBE、MOCVD和CBE等先进材料生长设备的创立和完善,大大促进了超薄层微结构材料的迅速发展,使微电子和光电子器件的设计从“杂质工程”发展到“能带工程”。主要介绍了国际上从晶格匹配材料体系到晶格失配的应变异质结构材料体系的研究成果及研究动向;简述了我国的超薄层微结构材料研究现状,并提出了一些意见。     

单结GaAs量子阱太阳能电池

介绍了采用金属有机化学气相沉积方法制备的单结GaAs量子阱太阳能电池.X射线双晶衍射表明电池中的材料缺陷较少,具有良好结晶质量与周期性.光谱响应实验表明量子阱结构的引入可以扩展吸收光谱.与无量子阱结构的电池相比,量子阱电池增加了输出电流,但同时也带来了开路电压的下降.量子阱电池在长波范围内短路电流明显增加,使得量子阱电池可以代替三结电池中的中间电池,优化电池结构设计,提高三结电池的转换效率.     

金属有机物化学气相沉积法沉积镍膜的影响因素

为了获得高速沉积镍膜的工艺参数，以羰基镍[Ni(CO)4]为前驱体，用金属有机物化学气相沉积法进行试验，以SEM，DSC，XRD测试分析技术探讨了载气、温度和羰基镍的摩尔分数对沉积速率的影响；也探讨了温度及羰基镍的摩尔分数对镍膜微观形貌的影响。结果表明，以氩气为载气比氦气为载气更容易获得高沉积速率；在沉积温度为150℃左右可获得沉积速率较快、微观形貌较好的薄膜；随羰基镍摩尔分数的增加，沉积速率也明显增大，同时薄膜的微观形貌也变得较为粗大，但达到30％之后，沉积速率增速减缓。     

有机超晶格结构的制备及其量子阱结构电致发光器件

利用高真空多源型有机分子沉积系统制备了由８－羟基喹啉铝（Ａｌｑ３）和叔丁基联苯基呃二唑（ＰＢＤ）交替生长的有机超晶格结构，小角Ｘ射线衍射分析表明，有机超晶格结构具有良好的、完整的周期性结构，并且界面质量很好。从光致发光及电致发光测量中发现，对于由以上两种材料制备的有机量子阱结构，激发态能量随着Ａｌｑ３层厚度的变薄发生了向高能方向移动。电致发光测量中也发现谱线在室温下有窄化现象。     

用MOCVD法在LiGaO2(001)上生长GaN的研究

LiGaO2单晶是目前所知的GaN最为理想的衬底材料，本研究用金属有机物气相沉积法（MOCVD）在LiGaO2(001)衬底上进行了外延生长GaN膜的试验，生长出了表面较为平整的GaN外延膜。应用原子力显微镜（AFM）、X射线粉末衍射（XRD）和高分辨X射线双晶衍射分别对衬底对外延膜和衬底材料进行了分析测试。结果表明，用MOCVD法可以在LiGaO2(001)衬底上生长出较高质量的无掺杂GaN(0001)外延膜。但由于MOCVD法是在高温还原气氛中生长GaN外延膜的，LiGaO2在这种气氛中不够稳定，实验发现衬底材料在生长过程中部分样品发生开裂，但没有发生相变。     

制备金属有机化合物的隔氧,隔水操作法

由于大多数金属有机化合物对空气中的水份和氧气十分敏感,如氧化(甚至自燃)、分解等。所以,必须采取特殊的技术进行操作。根据文献介绍,结合我们近几年来的工作经验,对金属有机化合物合成和分析的操作方法介绍如下。一、不稳定金属有机化合物的一般操作方法许多金属有机化合物主要对水、空气、光及热不稳定。为此,对这些化合物要防止     

MOVPE grown self-assembled and self-ordered InSb quantum dots in a GaSb matrix assessed by AFM, CTEM, HRTEM and PL

Self-assembled InSb quantum dots (QDs) were grown by metal-organic vapour phase epitaxy (MOVPE) in a GaSb matrix. Atomic force microscopy (AFM), conventional diffraction contrast transmission electron microscopy (CTEM), high resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) were used for the assessment of the QDs. Reductions in the ^III/_V ratios and growth rates resulted in a change of the morphology of the InSb islands from hillocks without facets, and a low level of order to dumbbell shaped islands with distinct facets and a higher level of order.     

Characterization of InP and GaAs films by contactless transient photoconductivity measurements

The characterization of III-V semiconductor films by contactless and non-invasive conductance and transient photoconductance measurements in the microwave frequency range were investigated. It was shown that the conductivity (of a GaSb film) and the majority carrier mobility (of GaAs and InP films) can be determined. Besides, information on charge carrier transport, in particular at the surface is obtained.     

Quantum dots fabricated by selective area MOVPE and their application to single electron devices

A novel method of formation of uniform GaAs quantum dot (QD) structures, using selective area metalorganic vapour phase epitaxy (SA-MOVPE), and their application to single electron transistors (SETs) are demonstrated. The SiN _x -coated substrates having a wire-like opening with three prominences are used. The wire-like opening is aligned in the [110] direction, which corresponds to channel region of SET. AlGaAs/GaAs modulation-doped heterostructures are grown on these substrates. Due to three prominences on the wire, the quasi-one-dimensional electron gas (Q-1DEG) channel, having a periodic variation in its width, are naturally formed. This leads to the formation of a quantum dot near the central prominence and two tunneling barriers beside the dot, which are connected to quantum wires.I _D−V _G characteristics under constant source-drain bias condition show clear conductance oscilations near the pinch-off, and oscillations are observed up to 65 K.I _D−V _DS characteristics measured at 2·1 K show clear Coulomb blockade. The results indicate the formation of SET by SA-MOVPE. Using similar method, resistance-load single electron inverter circuit is also fabricated.     

InAs/GaAs multiple quantum dot structures grown by LP-MOVPE

Structures with self-organised InAs quantum dots in a GaAs matrix were grown by the low pressure metal–organic vapour phase epitaxy (LP-MOVPE) technique. Photoluminescence and atomic force microscopy were used as the main characterisation methods for the growth optimisation. The properties of multiple-stacked quantum dot structures are influenced by the thickness of the GaAs separation layers (spacers) between quantum dot-containing InAs layers, by the InAs layer thickness, by arsine partial pressure during growth, and by group III precursor flow interruption time.     

GaAs/AlGaAs heterostructure nanowires studied by cathodoluminescence

In this report we explore the structural and optical properties of GaAs/A1GaAs heterostructure nanowires grown by metalorganic vapour phase epitaxy using gold seed-particles. The optical studies were done by low-temperature cathodo- luminescence （CL） in a scanning electron microscope （SEM）. We perform a systematic investigation of how the nanowire growth-temperature affects the total photon emission, and variations in the emission energy and intensity along the length of the nanowires. The morphology and crystal structures of the nanowires were investigated using SEM and transmission electron microscopy （TEM）. In order to correlate specific photon emission characteristics with variations in the nanowire crystal structure directly, TEM and spatially resolved CL measurements were performed on the same individual nanowires. We found that the main emission energy was located at around 1.48 eV, and that the emission intensity was greatly enhanced when increasing the GaAs nanowire core growth temperature. The data strongly suggests that this emission energy is related to rotational twins in the GaAs nanowire core. Our measurements also show that radial overgrowth by GaAs on the GaAs nanowire core can have a deteriorating effect on the optical quality of the nanowires. Finally, we conclude that an in situ pre-growth annealing step at a sufficiently high temperature significantly improves the optical quality of the nanowires.     

Electrooptical properties of GaNAs/GaAs multiple quantum well structures

The electrooptical properties of the GaNAs/GaAs multiple quantum well structures have been studied using the photoreflectance spectroscopy from 20 K to room temperature. Above the band gap energy of GaAs, Franz–Keldysh oscillations were observed. The period of the Franz–Keldysh oscillations decreased slightly with decreasing temperature, and indicated that the corresponding space charge distribution varied slowly with temperature. The modulated quantum well transition features were observed below the band gap energy of GaAs. A matrix transfer algorithm was used to calculate the quantum well subband energies numerically. The band gap energy and the electron effective mass of the GaNAs/GaAs system were adjusted to obtain the subband energies to best fit the observed quantum well transition energies.     

Efficient and uniform production of III-nitride films by multiwafer MOVPE

We present results on the growth of Ga–In–Al–N films in multiwafer Planetary Reactors® with 7×2 in. wafer capacity. The unique design of these reactors allows us to combine high efficiency (Ga efficiency in GaN around 30%) and excellent uniformity. Thickness uniformities better than ±5% on a 2 in. wafer are routinely obtained. Compositional uniformity of GaInN is better than 2 nm. Wafer-to-wafer and run-to-run reproducibility concerning thickness and composition is within the 1% range. Besides this, the material grown also has a high purity. Hall mobilities higher than 500 cm² V⁻¹ s⁻¹ are obtained for GaN. Furthermore, the design of the reactors is dedicated to the growth of complex nitride heterostructures. Fast switching manifolds for various group III precursors and different carrier gases allow a flexible design of the growth runs including nucleation, bulk layers (doped/undoped) and quantum wells. The extremely low thermal mass of the reactor permits very rapid changes of the deposition temperature between room temperature and 1300°C (optional: 1600°C). Of course p- and n-type doping is also possible. Doping uniformities are below 1% indicating extremely uniform wafer temperatures. The results demonstrate that Planetary Reactors® are reliable and efficient tools for the mass production of blue-green optoelectronic devices.     

GaAs的ICP选择刻蚀研究

选择刻蚀在ＧａＡｓ工艺中是非常重要的一步。由于湿法腐蚀存在钻蚀和选择性差,且精度难以控制,因此有必要进行干法刻蚀的研究。虽然采用反应离子刻蚀（ＲＩＥ）、磁增强反应离子刻蚀（ＭＥＲＩＥ）可以进行选择刻蚀,但是这两种方法在挖槽时会对器件造成较大损伤,影响器件性能。感应耦合等离子刻蚀（ＩＣＰ）是一种低损伤、高刻蚀速率高选择比的刻蚀方法,在ＧａＡｓ器件的制造中有突出的优点。本工作进行ＧａＡｓ／ＡｌＧａＡｓ     

MOVPE growth and characterization of AlxGa1-xN

AlGaN is an important material in the design of nitride devices. However, little is known concerning its growth with high Al contents. We have studied the growth of Al_xGa_1-xN epilayers on c-face sapphire by low pressure MOVPE (76 Torr), using triethylgallium, trimethylaluminum and ammonia as precursors. The solid versus gas phase composition relationship was determined experimentally and was fitted using a kinetic model. Then the structural properties of the layers (x=0–1) were studied, using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. We demonstrate that at high Al content, the buffer layer defects are replicated into the AlGaN layer.