Optimization of ohmic contact for AlGaNGaN HEMT by introducing patterned etching in ohmic area.pdfVIP

Solid-State Electronics 129 (2017) 114–119 Contents lists available at ScienceDirect Solid-State Electronics journal homepage: /locate/sse Optimization of ohmic contact for AlGaNGaN HEMT by introducing patterned etching in ohmic area q Wang Chong ?, Zhao Meng-Di, He Yun-Long, Zheng Xue-Feng, Wei Xiao-Xiao, Mao Wei, Ma Xiao-Hua, Zhang Jin-Cheng, Hao Yue Key Lab of Wide Band Gap Semiconductor Materials and Devices, Xi’an 710071, China The School of Microelectronics, Xidian University, Xi’an 710071, China article info Article history: Received 21 July 2016 Received in revised form 23 November 2016 Accepted 1 December 2016 Available online 2 December 2016 The review of this paper was arranged by Prof. E. Calleja Keywords: AlGaNGaN HEMT Ohmic contact Patterned etching Surface morphology abstract In this paper, the ohmic contact of AlGaNGaN HEMT was optimized by introducing patterned etching in ohmic area, and the conventional structure and whole etching structure were investigated for comparison. The contact resistance decreased from 0.46 X mm for conventional to 0.35 X mm and 0.18 X mm respectively for the whole etching and patterned etching structures. The current-voltage characteristics between the ohmic electrodes presented sharper slope, higher saturation current and lower knee voltage on patterned etching structures. After Cl2 plasma etching on ohmic area surface of AlGaN, the surface oxide layers and the pollutants were removed, therefore, the surface roughness of the ohmic metal reduced obviously, and the surface morphology improved. Meanwhile, the side area induced in patterned etching provided more extra contact area, which increased the tunneling current. The different apertures and the duty factor of patterned etching were investigated, and the results indicated that the quantity of side area produced in patterned etching dominated the reduction effect of ohmic contact resistance. ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction GaN material and its