GaP样品测试电极的制备

本文介绍了采用ｖａｎｄｅＰａｕｗ法测量ＧａＰ材料电学性能参数时，电极材料的选取及实现电极与样品良好欧姆接触的电极制备条件。     

p型GaP与Pd/Zn/Pd欧姆接触的冶金性质及界面特性

用扫描电镜、X射线衍射谱、能量色散谱及Ar~+离子溅射刻蚀的各元素的俄歇剖面分布,对Pd为基底的P型GaP的欧姆接触层的性质进行了研究。从而揭示了这种金属──半导体接触层形成良好欧姆电极的表面形貌、相变反应、界面状态及各冶金成份在界面层中的变化规律。     

Ag与p型GaP欧姆接触的表面特性分析

在p型GaP表面制作Ag电极,并利用退火环境令金属和半导体的接触界面产生良好的欧姆接触。通过扫描电子显微镜(SEM)、俄歇电子能谱(AES)以及X射线光电子能谱(XPS)的表征分析与对比,研究了不同退火环境对欧姆接触表面特性的影响。结果表明:退火时间过短,获得能量自由移动的原子移动面积小,不利于提高样品表面致密性;退火温度过高,欧姆接触表面的晶粒又容易发生球聚现象,造成样品表面的粗糙程度加剧。另外,在退火过程中,发生的相互扩散、形成化合物和合金相以及氧化反应也会对欧姆接触表面特性产生影响。其中,氧化反应较其他反应更为剧烈,对比接触电阻率的影响更大。因此,适宜的退火环境和有效控制氧化反应是增强欧姆接触性能的关键。     

Au—Zn／Au—Sb／GaP欧姆接触的研究

本文报导了Au-Zn/Au-Sb/GaP体系在520℃～560℃合金化温度下能得到较好的欧姆特性,观察到欧姆接触特性与合金化后界面形成的不规则小岛密切相关;从理论上解释了小而密的小岛能得到较低的比接触电阻的事实。同时,提出了Au-Zn/Au-Sb/GaP体系呈现良好欧姆接触的微结构模型。     

欧姆接触镍电极的研究

对镍电极浆料进行了实验研究。材料配方的选择和工艺的优化是实验的关键。实验中用玻璃粉和硼粉作为镍电极浆料的粘合剂和抗氧化剂，其中镍粉的质量分数不得低于65％，研制出的镍浆料可在大气中于810℃烧结在PTC等半导瓷上构成电极。通过扫描电镜(sEM)可以发现镍电极能牢固地附着在陶瓷体上并具有良好的欧姆接触性能。     

空气中烧成锌电极浆料的研究

半导瓷用锌电极浆料可在空气中烧成。材料配方的选择和工艺的优化是实验的关键。实验中以硼硅铅玻璃和金属有机化合物作为锌电极浆料的粘结剂和抗氧化剂，取得了良好的效果。     

n型6H-SiC体材料欧姆接触的制备

本文报道了采用Au／NiCr在n型6H－SiC体材料上制备欧姆接触的实验结果，依次蒸发NiCr合金（重量百分比为80％Ni：20％Cr）和金层，高温退火后形成欧姆接触，用改进的四探针法测得最小比接触电阻为8.4e-5·cm2．达到了应用的要求．     

大功率半导体激光器电极失效机理研究综述

大功率半导体激光器具有体积小、重量轻、转换效率高等优势,在工业加工、军事国防、医疗美容等各个领域具有广泛的应用。然而,大功率半导体激光器仍然受到电极失效的影响,导致其可靠性下降,使用寿命变短。本文首先阐述了大功率半导体激光器电极的失效机理;其次,介绍了电极的制备与欧姆接触评估方法,以及电极的失效分析手段方法,最后归纳了欧姆接触工艺的改良方法。在本文研究过程当中,归纳总结了目前学者们对于欧姆接触不良研究的相关进展,对进一步解决电极失效,提高大功率半导体激光器的可靠性具有重要的意义。     

P－GaP中离子注入缺陷的形成

研究了Ｚｎ~＋离子注入ｐ－ＧａＰ半导体所引起的缺陷。在电流密度为０．０３μＡ／ｃｍ~２下，将注入Ｚｎ~＋离子剂量为１×１０１~（１４）离子／厘米~２的ＧａＰ样品腐蚀出蚀坑后用ＳＥＭ观察，结果表明，在离子注入区域有缺陷形成。     

Degradation of GaP:N LEDs

The degradation of light output with operating time has been studied for nitrogen doped GaP light emitting diodes fabricated from vapor phase epitaxial material. The degradation is found to saturate at a non-zero value of efficiency. The process is characterized in terms of a degradation rate constant and the saturation value of efficiency. The rate is found to be a strong function of current density during operation and to a lesser degree materials parameters such as dislocation density. The saturation value appears to be independent of these parameters. The degradation is specifically associated with a decrease in the minority carrier lifetime in the p-side of these diffused LEDs. A model for the generation of non-radiative recombination centers which describes the degradation process quantitatively is presented.     

Quantitative esr analysis of deep defects in LEC-grown GaP

Defects in LEC GaP have been analyzed quantitatively using an ESR method. Transition-metal impurities and native defects were studied in as-grown crystals. The antisite defect, P_Ga, and the isolated gallium vacancy, V_Ga, were emphasized since no other method has given definite, quantitative information on these defects. P_Ga antisites are present in some Cr-doped and some Zn-dopeii samples in concentrations high enough to affect their electrical properties. V_Ga was not detected in as-grown crystals indicating that V_Ga concentrations are smaller than the antisite concentrations at least in p-type material. Typical ESR detection., limits for transition-metal impurities are in the middle 10¹⁴ cm⁻³ range. The method is especially sensitive to Fe traces which were observed in all the samples studied. Work performed while the author was a visiting scientist at TAF Freiburg,     

p型GaN基器件的欧姆接触

宽带隙的GaN具有优良的物理和化学性质,己成为半导体领域研究的热点之一。p型GaN的欧姆接触问题制约了GaN基器件的进-步发展。本文首先介绍了欧姆接触的原理及评价方法,详细讨论了实现良好的p型GaN欧姆接触的主要方法是采取表面处理技术、选择合适的金属电极材料和进行热退火处理,以及研究进展情况。最后指出目前存在的问题并提出今后的研究方向。     

太阳能电池埋栅电极制造新技术

介绍了用电镀法来制造太阳能电池的埋栅电极方法,对各镀层所需的溶液配制及操作工艺参数进行了详细的说明,通过与传统工艺的比较,可以看出采用新技术制造太阳能电池片,可有效降低栅线电极成本,提高电池片转换效率。     

Mg在InGaAlP及GaP材料中的掺杂行为

利用 SIMS分析技术 ,研究了在 In Ga Al P和 Ga P材料中 ,MOCVD工艺参数对 Mg的掺杂行为的影响 .实验结果表明 ,在较高温度下 ,Mg在生长表面的再蒸发决定了 Mg的掺杂浓度随衬底温度增加呈指数下降 ;而当载流子浓度饱和时 ,杂质 Mg在材料中的置换填隙机制使得 Mg的激活率随 Cp2 Mg流量的再增加反而下降 .同时通过计算得到 Mg在 In Ga Al P及 Ga P中的再蒸发激活能分别约为 0 .9e V和 1.1e V     

Electrical characteristics of In/ITO p-type ohmic contacts for high-performance GaN-based light-emitting diodes

We have investigated the annealing-induced improved electrical properties of In(10 nm)/ITO(200 nm) contacts with p-type GaN. The contacts become ohmic with a specific contact resistance of 2.75×10^–3 Ω cm² upon annealing at 650 °C in air. X-ray photoemission spectroscopy (XPS) Ga 2p core levels obtained from the interface regions before and after annealing indicate a large band-bending of p-GaN, resulting in an increase in the Schottky barrier height. STEM/energy dispersive X-ray (EDX) profiling results exhibit the formation of interfacial In-Ga-Sn-oxide. Based on the STEM and XPS results, the ohmic formation mechanisms are described and discussed. It is also shown that patterning by nano-imprint lithography improves the light output power of blue LEDs by 18–28% as compared to that of LEDs fabricated with unpatterned In/ITO contacts.     

Growth and properties of VPE GaP for green LEDs

The PH₃-HCl-Ga-H₂ technique for VPE growth of GaP is described. The influence of various growth parameters, including substrate temperature, orientation, and PH₃ flow rate on morphology and growth rate are described. For both VPE and LPE nitrogen doping is known to be a major factor in obtaining high green luminescence efficiency. The major emphasis of this paper is an examination of the effect of nitrogen concentration in the range less than 10¹⁹ cm⁻³ (using the Lightowlers correction factor) on the growth process and materials properties, such as defect structure, photoluminescence spectra (at 300 and 77K) and photoluminescence intensity and lifetime. The LED device performance (B/J and efficiency) is used as the final test of material quality. Nitrogen is found to be incorporated far in excess of the solubility limit, and the solid gas distribution coefficient for nitrogen is found to increase rapidly with decreasing temperature below 840°C . The optimum nitrogen concentration for high diode efficacy, photoluminescence intensity, and lifetime is found to be approximately 5 × 10¹⁸ cm⁻³, where diodes fabricated by Zn diffusion into the VPE GaP have efficiencies at a current density of 10 A/cm² of 0.1%, comparable to the state-of-the-art in the more widely used grown p-n junctions using LPE.     

溶剂热条件下单质直接反应合成GaP纳米晶

在苯热条件下,以金属镓和白磷为原料直接反应合成了GaP纳米晶,并研究了反应温度对GaP纳米晶物相的影响。微观形貌观测结果则表明,在400℃合成的GaP纳米晶体粒度均匀,而且团聚现象较少。当温度为300℃时,GaP纳米晶的结晶质量较差,而当温度升高到500℃时,GaP纳米晶的结晶完整性得到改善,但是颗粒团聚现象变得比较严重。     

短波CMT红外光导探测器延伸电极的改进

针对短波CMT红外光导探测器出现的拖尾问题,找到其拖尾的原因:过渡电极的功函数过大.为此,在原来Cr/Au电极的基础上,提出了In/Au+Cr/Au电极初步解决了拖尾问题,但是在工艺上出现了In聚球现象,影响器件的稳定性.又提出Ti/Au电极,比较好的解决了拖尾问题和In/Au+Cr/Au电极带来的工艺问题.