A Review of Reliability and Failure Mechanisms of SiC MOSFETs and GaN HEMTs in High-Power-Density Power Electronic Systems

Abstract

Wide-bandgap (WBG) semiconductor power devices, particularly silicon carbide (SiC) MOSFETs and gallium nitride (GaN) high-electron-mobility transistors (HEMTs), have attracted considerable attention in high-power-density power electronic systems because of their superior electrical and thermal properties compared with conventional silicon devices. However, the reliability of these devices has become a major obstacle to their extensive use in industry. This paper carefully organizes the main reliability modes and failure mechanisms of SiC MOSFETs and GaN HEMTs. These include gate oxidation deterioration, threshold-voltage instability, dynamic on-resistance increase, current collapse, bipolar deterioration, thermal stress and short-circuit degradation. How to evaluate reliability is also discussed, including accelerated bias test, pulsed electrical characteristic evaluation, transient tracking analysis, power cycling and life prediction. The review shows that the reliability of SiC MOSFET is mainly limited by the SiC/SiO₂ interface, the integrity of gate-oxide and the degradation of bipolar. On the other hand, GaN HEMTs is very sensitive to the trap of surface, barrier and buffer. Further analysis shows that the phenomenon of insulator breaking with time varies with the structure of gate. TDDB of common gate-oxide is directly related to MIS-gate GaN HEMTs, while p-GaN devices are affected by gate-barrier degradation, increased leakage current and catastrophic gate breakdown. The fatigue of Packaging is a common problem that both technologies can shorten the life. Finally, in order to make a robust WBG power conversion system, the reliability requirements for various purposes, unresolved life modeling topics and future research directions are confirmed.