Design and Fabrication of GaN-Based SBDs on Silicon for Suppressing Surface Leakage Current

• Main Authors: Wu, Ping Sheng, 吳秉昇
• Other Authors: Hsu, Shuo Hung
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/14884989827156989253

碩士 === 國立清華大學 === 電子工程研究所 === 103 === AlGaN/GaN HEMT have attracted considerable interests for high speed and high power switching application due to the outstanding electronic properties including high sheet charge density (>1013 cm-2) of the two dimensional electron gas (2DEG), high thermal conductivity of GaN (>2 Wcm-1k-1) and high breakdown field (3.3 MV/cm), which allows to fabricate devices with breakdown voltages in the order of hundreds and even up to thousands of volts. However, one of the most critical issues to be solved is the surface leakage current, which is mainly related to reliability and stability for power electronics applications. This thesis focuses on AlGaN/GaN heterojunction Schottky barrier diodes (SBDs) on Si substrate for power electronics applications. For high power applications, the surface control process was investigated to suppress leakage current in GaN-on-Si devices by using two different approaches, including a passivation first process and a nitrogen plasma treatment process. Both two approaches are proposed to protect surface from producing N-vacancy defects during high temperature annealing for ohmic contact formation and further suppress the leakage current by recovering nitrogen-vacancy-related defects. First, a passivation first approach is proposed to reduce the surface leakage current from ~10-9 A to ~10-11 A and reduce the sheet resistance up to 70% compared with the SBDs without passivation first. Second, the devices with the nitrogen plasma treatment show a reduced VON from 1 V to 0.7 V for 12-nm recess SBDs and a reduced VON from 0.8 V to 0.4 V for 30-nm recess SBDs, comparing with that of the devices without nitrogen plasma treatment. We also investigated the impact of the plasma power on the device characteristics. With a higher power of plasma treatment on anode region, the turn-on voltage can be reduced with slightly degradation of reverse leakage current. On the other hand, the plasma treatment on the drift region could reduce the reverse leakage current.