AlGaN紫外探测器p电极的Ni/Au/Ni/Au欧姆接触结构研究

研究了AlGaN半导体p电极的Ni/Au/Ni/Au接触结构的性能和组织结构。退火前，p电极接触具有明显的整流特性。经空气中550℃/3 min一次退火和N2 气氛中750℃/30 s二次退火后，电极呈现出了良好的欧姆接触。采用扫描电镜(Scanning Electron Microscope, SEM)、透射电镜(Transmission Electron Microscope, TEM)、能量分散谱仪(Energy Dispersive Spectrometer, EDS)和X射线光电子能谱(X-ray Photoelectron Spectroscopy, XPS)观察了电极退火后金-半界面微结构的演化过程。结果表明，完全退火后的p电极界面及金属层出现了明显的互扩散和界面反应现象；金-半界面上形成了存在良好共格/半共格关系的外延结构。初始沉积的金属电极分层现象消失，形成了单一的电极结构。Ni向外扩散并与O发生反应，Au扩散至p-GaN 表面。在金-半接触界面上，Ga扩散至金属电极，造成界面附近的金属层中富集Au和Ga元素；Au和Ni明显扩散至半导体表层，在金-半界面附近形成了Au、Ga和Ni富集现象。这些现象应该对于降低势垒高度和形成欧姆接触具有重要作用。

Abstract

The performance and structure of Ni/Au/Ni/Au contact of p electrode of AlGaN semiconductor are studied. Before annealing, the p electrode has obvious rectifying characteristics. After being annealed in air at 550℃ for 3 min and then being annealed in N2 at 750℃ for 30 s, a good ohmic contact is obtained. To uncover the ohmic contact forming mechanism of this structure, the Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Energy Dispersive Spectrometer (EDS) and X-ray Photoelectron Spectroscopy (XPS) are used to study the microstructure evolution of metal-semiconductor interface. The results show that the metal schemes change sharply and an interdiffusion and interface reaction happens during annealing. The as-deposited four-layer electrode is missing and is replaced by a single metal layer. A coherent or semi-coherent relationship is established at the interface. Thus, Ga diffuses to the metal electrode and Au and Ni diffuse into the upper layer of the semiconductor at the interface. Ga, Au and Ni are enriched across the interface. Ni has an outward diffusion and reacts with O. Au has an inward diffusion to the p-Ga surface. All of these phenomena are critical to the formation of the ohmic contact.

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祁昌亚, 胡正飞, 张燕, 李向阳, 张振, 童慧. AlGaN紫外探测器p电极的Ni/Au/Ni/Au欧姆接触结构研究[J]. 红外, 2016, 37(2): 22. QI Chang-ya, HU Zheng-fei, ZHANG Yan, LI Xiang-yang, ZHANG Zhen, TONG Hui. Research on Ni/Au/Ni/Au Ohmic Contact Structures of p-AlGaN Ultraviolet Detector[J]. INFRARED, 2016, 37(2): 22.

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