CdZnTe晶体表面Au电极薄膜的制备及其欧姆接触性质

为了研究不同制备工艺对电极欧姆接触特性的影响, 分别采用真空蒸发法、溅射法及化学沉积法在CdZnTe晶片表面制备了Au薄膜电极, 通过测试样品的SEM、I-V曲线及交流阻抗谱, 研究了不同电极制备工艺及退火处理对Au薄膜电极的微观结构及欧姆接触特性的影响。结果表明化学沉积法制备的Au薄膜表面更加平整、致密, 接触势垒的高度较低, 电极欧姆接触特性最好。退火处理可以改善电极的欧姆接触特性, 100℃退火后, 化学沉积法制备的Au电极的欧姆系数由0.883提高至0.915, 势垒高度由0.492降低至0.487 eV。交流阻抗谱分析表明, 化学沉积法制备电极具有最低的接触势垒, 这与界面处晶片表面的掺杂及缺陷的变化有关。     

Au电极与CdMnTe晶体的表面接触电阻率研究

采用圆形传输线模型研究了金(Au)电极与碲锰镉(CdMnTe)晶体的欧姆接触特性,Au电极采用AuCl3化学镀金法制备,计算了其接触电阻率。实验探讨了表面处理和退火对Au/CdMnTe接触电阻率的影响。结果表明,CdMnTe晶体经过化学抛光和化学机械抛光后Au/CdMnTe的接触电阻率分别为544.5和89.0Ω·cm2。通过AFM与XPS分析了晶体表面的形貌与成分,发现表面粗糙度和富Te成分对CdMnTe薄层电阻和载流子传输长度有较大的影响,决定了接触电阻率的大小。在150℃空气气氛退火1h后,经CP和CMP表面处理的样品,Au/CdMnTe接触电阻率均减小,分别为313.6和30.2Ω·cm2。退火促进了Au向CdMnTe晶体的扩散,使接触电阻率进一步降低,欧姆接触性能提高。     

不同沉积工艺下Au/P-CdZnTe接触界面的研究

采用超声波扫描(SAM)、俄歇电子能谱分析技术(AES)、电极粘附力测试和I-V特性测试等方法研究了化学沉积、溅射和真空蒸发三种不同沉积工艺条件下Au/p-CdZnTe接触界面的各种特性.通过实验结果可以看出,化学法沉积的Au电极能形成较好的欧姆接触特性,但其操作工艺不容易控制,电极接触层均匀性较差,在器件使用过程中,容易引起电极的退化;溅射沉积的Au电极有着较好的附着力,但对CdZnTe表面的损伤较大,欧姆接触特性较差;真空蒸发法沉积的Au电极,有着较好的欧姆接触特性,且其电极接触层也较为均匀,只是电极附着力相对较小,但可以通过合适的退火工艺进行改善.     

Au/p-CdZnTe欧姆接触的电学测量及界面特性分析

采用化学镀金法在高阻p-CZT(CdZnTe)晶片表面制备Au电极,并用改进的圆环传输线模型(Ring-CTLM)测量了CZT电极的接触电阻,探讨了大气气氛下退火温度对CZT电极欧姆特性的影响.实验结果表明,200℃退火可以显著改善欧姆特性,使接触电阻率ρc显著减小,采用Ring-CTLM模型测得CZT与金电极接触电阻率为0.1524Ω·cm2.通过XPS分析了CZT与Au电极接触界面的成分,发现在Au/p-CdZnTe界面处形成了CdTeO3层,该界面层可起到载流子复合中心的作用,构建的新模型很好地解释了化学镀金法在p-CdZnTe晶片表面形成欧姆接触的机理.     

Ti/Al/Ni/Au在N-polar GaN上的欧姆接触

N-polar GaN以其特有的材料特性和化学活性日益受到研究者关注,而N-polar GaN上欧姆接触也成为研究的热点。以Ti/Al/Ni/Au作为欧姆接触金属,分析了N-polar GaN上欧姆接触的最优退火条件,并借助剖面透射电子显微镜(TEM)和能量色散X射线能谱仪(EDX)研究了金属和N-polar GaN之间的反应生成物。结果表明,当退火温度升高到860℃时,可得到比接触电阻率ρc为1.7×10~(-5)Ω·cm~2的最优欧姆接触特性。TEM和EDX测试发现,除了生成已报道的AlN,还会在界面处产生多晶AlO_x,两者共同作用会进一步拉高势垒,从而对N-polar GaN上欧姆接触产生不利影响。     

CdZnTe晶体欧姆接触电极的制备工艺研究

高阻CdZnTe晶体是X射线及γ射线探测最优秀的材料.制备CdZnTe探测器最关键的技术之一就是在CdZnTe表面制备出欧姆接触薄膜电极.关于在CdZnTe晶体表面制备接触电极用导电薄膜,大都是采用蒸发镀膜技术,膜层与CdZnTe晶体结合不很牢固.本论文主要开展了在CdZnTe晶体上欧姆接触电极的选材和制备工艺的研究.理论分析了金属与CdZnTe半导体的接触关系,根据影响因素选择Cu/Ag合金作为电极薄膜材料.利用射频磁控溅射法成功地在CdZnTe晶体上制备出Cu/Ag膜.研究发现Cu/Ag合金膜的电阻率随溅射功率的增大而增大、衬底温度的升高而降低.从理论上对这一规律进行了解释.     

Ti/Al/Ni/Au与n型GaN的欧姆接触研究

通过电流 电压 (I V)特性和传输线方法 (TLM )测量研究在n型GaN上淀积Ti/Al/Ni/Au电极形成欧姆接触的机制。Ni/Au作为Ti/Al的覆盖层起了阻止Ti ,Al,Au的互扩散及抗接触层氧化的作用。在 4 0 0℃到 90 0℃范围内 ,Ti/Al/Ni/Au与n型GaN的接触电阻随温度升高先略有上升 ,到 5 0 0℃以后单调下降。而表面形貌却在合金温度高于6 0 0℃以后随温度升高逐步变差。通过两步合金法得到了n GaN上Ti/Al/Ni/Au形成的接触电阻低达 9.6 5× 1 0 - 7Ωcm2 。最后还对两步合金法形成n GaN欧姆接触的机制进行了讨论。     

两步镀膜Ti/Al/Ti/Au的n型GaN欧姆接触研究

报道了一种可靠稳定且低接触电阻的n型GaN欧姆接触。首先在掺硅的n型GaN(3×1018cm-3)蒸镀Ti(30nm)/Al(500nm),然后在氮气环境530℃合金化3min,最后蒸镀Ti(100nm)/Au(1000nm)用于保护Al层不被氧化。该接触电极有良好的欧姆接触特性,比接触电阻率为8.8×10-5Ωcm2,表面平坦、稳定、易焊线,可应用于制作高性能的GaN器件.     

Au-CZT与Au/Cr-CZT接触性能比较

本文通过附着力测试,应力模拟和IV特性及多道能谱分析对Au-CZT与Au/Cr-CZT接触进行研究。结果表明采用Au/Cr复合电极可提高电极附着强度和热稳定性。在老化实验中,Au-CZT界面附着力下降了61.98%,而Au/Cr-CZT仅降低28%。Au/Cr电极器件的漏电流较低,241Am射线下能谱响应更佳。分析其原因可能是Au与CZT间的Cr层降低了接触层内的热应力,合金化过程促进了金-半界面的互扩散,使Au和CZT更易形成欧姆接触,综合考虑Au/Cr复合电极能获得比Au电极更理想的接触性能。     

金属/Hg1-xMnxTe接触的I-V特性研究

分别采用溅射和蒸发镀膜法在Hg1-xMnxTe试样表面形成了Au/Hg1-xMnxTe和Al/Hg1-xMnxTe接触,并用Aligent4155c I-V测试仪对其I-V特性进行了测量,随后对试样在10%NH4F:10%H2O2:H2O中进行了钝化处理,并对处理后的试样再次进行了I-V测量,对于测试结果用热电子发射-扩散理论进行了分析.结果表明:Au与Hg1-xMnxTe形成了良好的欧姆接触,而Al与Hg1-xMnxTe形成了具有整流特性的肖特基接触,其肖特基势垒的理论推算值为0.38eV.钝化处理后的试样,其表面漏电现象明显降低,Au/Hg1-xMnxTe接触的电流下降幅度在0.1V时最大,为76.1%;而Al/Hg1-xMnxTe接触在0.2V时最大,为93.2%.随着偏压的进一步增大,两种接触的电流减小的幅度都逐渐变小.     

Formation of WSi-based ohmic contacts to n-type GaAs

An outcome of the indirect doping concept conceived recently in NiGe-based Ohmic contacts has led to the development of annealed WSi-based Ohmic contacts to n-type GaAs for the first time. It was concluded that simultaneous addition of a “direct doping element” of Si in WSi_2.7 and an “indirect doping element (M)” such as Au, Pd, Cu, or Ag, was essential. The M(5 nm)/WSi_2.7(20nm)/W(50 nm) contacts showed Ohmic behavior after annealing with the lowest contact resistances of 0.4 Ω mm (6×10⁻⁶ cm²). In addition, the WSi-based contacts with a small amount of Au showed good thermal stability at 400 °C after contact formation. Microstructural analysis of the WSi contacts with Au showed formation of β-AuGa and WSi₂ compounds, which indicates that the Ohmic behavior would be due to heavy doping of Si at the GaAs surface induced by Ga out-diffusion. The mechanism of Ohmic contact formation of the present contacts agreed very well with that of the NiGe-based Ohmic contacts.     

Surface Effects of the HgI(2) Crystal Characterized by Spectroscopic Ellipsometry

We report on determination of the surface effects of mercuric iodide (HgI(2)) uniaxial HgI(2) optical parameters with a fixed-polarizer, rotating-polarizer, and fixed-analyzer spectroscopic ellipsometer (PRPSE) after chemical polishing. The characteristics of the chemical complex [KHgI(3), H(2)O] that forms on the HgI(2) surface during KI etching have been investigated over the spectral range from 400 to 800 nm. Surface roughness and effects of the ellipsometric parameters of HgI(2) were treated, and the thickness of the layer formed on the surface was determined and analyzed by PRPSE. The surface roughness was modeled with the Bruggeman effective medium approximation.     

超声物理气相沉积法制备（00l）取向HgI2膜的研究

超声波作用下,采用热壁物理气相沉积法在相对较低温度下(<90℃)成功制备了(00l)取向多晶碘化汞膜,分析了超声工艺对(00l)取向多晶碘化汞膜质量的影响.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、拉曼光谱仪(Raman)对(00l)取向多晶碘化汞膜进行了表征.结果表明,超声波作用下,相对较低的生长温度能够获得高质量(00l)取向多晶碘化汞膜,同时超声波工艺不仅能够明显改善多晶碘化汞厚膜的质量而且能提高生长速率.     

Preparation, Transmission Electron Microscopy, and Microanalytical Investigations of Metal-III-V Semiconductor Interfaces

Ohmic metallizations on semiconductors such as In_0.53Ga_0.47As and GaAs have been analyzed by cross-sectional transmission electron microscopy. To obtain a lattice image of multilayer structures in the high-resolution mode, a cross-sectional specimen preparation procedure was developed. The phase formation after thermal treatment of the ohmic contacts has been studied by applying different microanalytical techniques. The results have been utilized for improving the metallurgical stability and the electrical properties of the contacts.     

Spectroscopic ellipsometry of anisotropic materials: application to the optical constants of HgI2

A variable angle-of-incidence spectroscopic fixed-polarizer, rotating-polarizer, fixed-analyzer ellipsometer (PRPSE) across a spectral range from 300 to 800 nm is used to determine the optical properties of anisotropic uniaxial tetragonal red mercuric iodide (HgI(2)). For the first time, to our knowledge, the bulk crystal HgI(2) surface measured by ellipsometry was not subjected to potassium iodide cutting or etching. Measurements were made at an air-HgI(2) interface with the optic axis parallel to the sample surface. To determine the optical constants, we varied both the angle of incidence and the azimuth of the optic axis with the plane of incidence. The detailed formulas needed for reliable procedures for analyzing the data are presented. The ordinary and extraordinary complex indices of refraction, (n(o) - ik(o)) and (n(e) - ik(e)), respectively, are determined. Good agreement between PRPSE and the prism technique for the refractive index is observed. The surface aging effects of the ellipsometric parameters of HgI(2), during 30 h of exposure to air, were detected by PRPSE.     

AlGaN/GaN肖特基二极管中金属电极的制备方法研究

本文主要研究AlGaN/GaN二极管制备工艺中Ohmic Contact金属和Schottky Contact金属电极的制备,主要讨论了金属电极材料的选取,退火温度和退火时间对接触电阻的影响,最后得出了Ohmic Contact的比接触电阻和TiN的淀积参数。     

Si基n型GaN的欧姆接触研究

GaN材料在光电子器件领域的广泛应用前景使得金属与其欧姆接触的研究成为必然。本文对Si基n型GaN上的Al单层及Ti/Al双层电极进行了研究。通过对不同退火条件下的I U特性曲线 ,X射线衍射以及二次离子质谱分析 ,揭示了界面固相反应对欧姆接触的影响 ,提出了改善这两种电极欧姆接触的二次退火方法     

Thermal stability of N-polar n-type Ohmic contact for GaN-based light emitting diode on Si substrate

Thermal stability of N-polar n-type Ohmic contact for GaN light emitting diode (LED) on Si substrate was investigated. Al/Ti/Au were deposited as the contacts on the N-polar n-type GaN with and without AlN buffer layer on the surface, respectively, and both contacts exhibited Ohmic behaviors. The samples with AlN showed excellent Ohmic contact thermal stability when annealed below 700 °C, while the samples without AlN experienced serious degradation on electrical properties after being annealed in the temperature range of 250-600 °C. After the process of aging at 30 mA (155 A/cm²) and room temperature for 1000 h, operating voltage increase less than 0.05 V for LEDs with AlN but more than 0.45 V for LEDs without AlN. Therefore, we conclude that the existence of AlN buffer layer is a key of forming high stable Ohmic contact for GaN-based vertical structure LED on Si substrate.     

镍基高温合金粉末制备技术的发展现状

粉末高温合金是先进航空发动机关键热端部件的优选材料,先进的粉末制备技术是获得高品质高温合金粉末、保证合金件质量的关键技术。近年来,我国在粉末高温合金的研发和生产技术方面都取得了突破性进展,成功研发出新一代粉末高温合金,形成了成熟的粉末高温合金生产工艺。在粉末制备技术方面,通过对高纯净母合金熔炼技术、先进雾化制粉技术和电选分离技术的深入研究,进一步发展了粉末纯净化制备技术,满足了我国航空发动机领域对粉末高温合金关键零部件的需求。简要回顾了国内外粉末高温合金的发展历程,分析了粉末高温合金中的缺陷来源及其对合金性能的影响,概述了我国镍基高温合金粉末制备技术的发展情况,讨论了未来高温合金粉末及其关键制备技术的发展方向。