ABSTRACT
Nowadays, GaN HEMT devices still cannot reach the theoretical brilliant performance due to reliability issues. Firstly, though GaN is a high-temperature-tolerant material, for a Schottky contact device, the semiconductor–metal contact suffers degradation under high temperature. The performance of GaN devices also varies with different temperatures. Secondly, the current collapse effect significantly limits the current performance, which is mainly reflected in the fact that current performance of a GaN HEMT deteriorates after stress or at an AC condition compared to a DC condition. Finally, the prebreakdown phenomenon of a GaN HEMT limits further improvement of the breakdown voltage in a high-power field, which can be attributed to an electric field peak, bulk leakage, and the reverse piezoelectric effect. This chapter summarizes several degradation phenomena and mechanisms of GaN devices. Optimizing growth technology of materials to avoid defects and traps, novel device structure design like optimized Schottky contacts, addition of a new interlayer or a new material, and surface passivation are required.
