Surface Reinforcement Technology for Suppressing Hot-Carrier-Induced Degradations in p-GaN Gate Power HEMTs

Highly energetic "hot" carriers generated during both ON and semi-ON states have been identified as a predominant root cause of reliability issues in p-GaN gate power HEMTs. In this work, with plasma oxidation and high-temperature annealing, a surface reinforcement layer (SRL) is formed at the surface of both the p-GaN gate and the AlGaN barrier in the access region. At ON-state, the reinforced p-GaN surface exhibits enhanced immunity against hot-electron bombardment at the gate metal/p-GaN junction, and thus effectively prolongs the time-dependent-gate-breakdown (TDGB) lifetime. During the transient state of hard switching (i.e., the semi-ON state), the SRL formed at the AlGaN surface exhibits improved robustness under the stress of hot electrons generated from the channel. As a significant benefit, the dynamic ON-resistance degradation after long-term operation could be substantially suppressed.