Improved gate reliability of normally off p-GaN gate HEMTs with in situ SiN cap-layer

• Published in: Applied physics letters 2024-11, Vol.125 (19)
• Main Authors: Zhang, Ga, Zhao, Shenglei, Song, Xiufeng, Yu, Longyang, Sun, Xuejing, Cao, Chuangzhe, You, Shuzhen, Liu, Zhihong, Hao, Yue, Zhang, Jincheng
• Format: Article
• Language: English
• Subjects: Breakdown; Current leakage; Energy bands; Failure rates; Gallium nitrides; High electron mobility transistors; High temperature; Leakage current; MIS (semiconductors); Reliability; Semiconductor devices; Threshold voltage
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0237694

The gate reliability of p-GaN gate high electron mobility transistors (HEMTs) was investigated in this Letter. Compared with conventional p-GaN gate HEMT, the in situ SiN cap-layer on the p-GaN layer can lift up the energy band and form a metal–insulator–semiconductor structure. With the introduction of an in situ SiN cap-layer, the DC electrical characteristics and reliability have been significantly improved. The reverse gate leakage current is reduced by 3 orders of magnitude. The threshold voltage shifts from 1.67 to 3.25 V, the on-resistances increased from 8.7 to 9.9 Ω mm, and the gate breakdown voltage is improved from 10.2 to 16.3 V. After conducting time-dependent gate breakdown measurement and predicting lifetime with a 10-year failure rate of 63%, it is calculated that the maximum allowable gate voltage increased from 6.3 to 11.4 V. The 10-year gate voltage swing has improved from 4.63 to 8.15 V. In addition, the in situ SiN HEMT exhibits good stability under high temperatures and long-term stress tests. The experimental results demonstrate that the in situ SiN cap-layer offers significant advantages in gate reliability.