Degradation Mechanism of Pd/p-GaN Ohmic Contacts

Fan ZHANG; Rong-xin WANG; Si-yi HUANG; Ai-qin TIAN; Jian-ping LIU; Hui YANG

doi:10.37188/CJL.20210092

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Degradation Mechanism of Pd/p-GaN Ohmic Contacts

Luminescence Industry and Technology Frontier | 更新时间：2021-07-22

- Degradation Mechanism of Pd/p-GaN Ohmic Contacts
- Chinese Journal of Luminescence Vol. 42, Issue 7, Pages: 1065-1073(2021)
- 作者机构：
  
  1.中国科学院苏州纳米技术与纳米仿生研究所　纳米器件与相关材料研究部，江苏　苏州　 215123
  2.上海科技大学　物质科学与技术学院，上海　 201210
  3.中国科学院苏州纳米技术与纳米仿生研究所　纳米真空互联实验平台，江苏　苏州　 215123
- 作者简介：
- 基金信息：
  
  National Natural Science Foundation of China(11974378;61834008;61574160;61804164;61704184);National Key Research and Development Program of China(2017YFE0131500;2017YFB0405000;2017YFB0403101);Natural Science Foundation of Jiangsu province(BK20180254)
- DOI：10.37188/CJL.20210092
  CLC： O482.31
- Published：01 July 2021，
  
  Received：16 March 2021，
  
  Revised：04 April 2021，
扫描看全文
Fan ZHANG, Rong-xin WANG, Si-yi HUANG, et al. Degradation Mechanism of Pd/p-GaN Ohmic Contacts. [J]. Chinese Journal of Luminescence 42(7):1065-1073(2021)
DOI：

Fan ZHANG, Rong-xin WANG, Si-yi HUANG, et al. Degradation Mechanism of Pd/p-GaN Ohmic Contacts. [J]. Chinese Journal of Luminescence 42(7):1065-1073(2021) DOI： 10.37188/CJL.20210092.

摘要

近几年，Ⅲ-Ⅴ族半导体GaN由于其宽直接带隙，在高温、高功率器件方面得到了广泛研究。但是，目前GaN器件的性能依然受到了p型欧姆接触性能不良的限制，在长期使用过程或高温环境中激光器等器件性能退化严重。因此，获得性能优异的p-GaN接触仍然是一个巨大的挑战。虽然Pd基的金属体系已然在p-GaN获得了欧姆接触，但是Pd与GaN接触之后的微观结构及其高温特性尚不为人知。本文针对常用于p型GaN接触的第一层金属Pd材料，讨论了Pd/p-GaN接触界面的特性和退化机制。通过四探针测试仪、X射线光电子能谱(XPS)和原子力显微镜(AFM)实验测试和分析对比，发现Pd/p-GaN界面受到氧气和温度影响的退化过程。高温退火在界面处促成Ga-Pd合金相生成利于形成良好的接触，但是在有氧参与的情况下，金属的氧化反应超越其他因素成为主导，致使界面和性能发生明显的退化。温度越高退化越严重，甚至表面形貌状态完全改变，由平滑的原子台阶形貌转化呈现出树枝状晶粒状态。因此，保持Pd与p-GaN界面清洁、控制界面的氧成分不仅是形成合金态获得良好接触的关键，而且也关系着器件的长期稳定和可靠，是防止器件性能衰减和退化要害所在。

Abstract

GaN-based wide bandgap semiconductors and devices have been quickly emerging as a new frontier and cutting-edge technique. It is necessary to fabricate Ohmic contact for GaN device application. Pd is one of candidate metals for fabricating metal/p-GaN Ohmic contacts. Under the identical preparation conditions

different thickness Pd films were sputtered on p-GaN epilayers in sputtering chamber directly connected with MOCVD growth system. After the metal deposition

the samples were then annealed at 300 ℃ and 600 ℃ in ambient atmosphere of N

∶O

=4∶1 or under vacuum conditions for 90 s. They were measured and characterized by four-probe Van de Pauw

X-ray photoelectron spectroscopy(XPS)

and atomic force microscopy(AFM). It is found that the electrical properties and surface morphologies of samples were dependent on annealing ambient atmosphere and heat treatment temperature conditions. When the samples were annealed at 600 ℃ under high vacuum conditions

Ga can be diffused out from Pd/p-GaN interface. It would be helpful to make Ga and Pd reactive to become alloy as well as to produce Ga vacancy for Ohmic contact. While the samples were annealed in N

∶O

=4∶1 environment

however

oxidation of metal Pd and Ga becomes a dominant factor resulting in degradation of the Ohmic contacts.The higher the annealing temperature in oxygen environment

the worse the electrical properties. Surface morphologies of the annealed samples were completely changed from a smooth atomic step morphology to a dendritic polycrystal grain state if oxygen was participated into the interface during the annealing process. Therefore

avoiding oxygen incorporation at Pd/p-GaN interface shall be a key role in forming alloy and Ohmic contact

which favors the stability and reliability of device performance.

关键词

p型GaN欧姆接触XPS界面

Keywords

p-GaNOhmic contactXPSinterface

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Rong-Xin WANG

Si-yi HUANG

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Related Institution

Vacuum Interconnected Nanotech Workstation， Suzhou Institute of Nano-Tech and Nano-Bionics， Chinese Academy of Sciences

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State Key Laboratory of High Power Semiconductor Lasers, Changchun University of Science and Technology

State Key Laboratory of Electronic Thin Films and Integrated Devices, Zhongshan Institute, University of Electronic Science and Technology of China

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