Observation of avalanche breakdown characteristics in quasi-vertical GaN-on-Si trench MOSFETs

We report avalanche breakdown characteristics of normally off quasi-vertical GaN-on-Si trench MOSFETs. Initially, the avalanche breakdown of p–n diode with low-damage mesa etching on the n+-p-n−-n+ grown epitaxial structure was confirmed by positive temperature coefficient and uniform GaN band edge emission around mesa edge-side. For trench MOSFETs, an improved trench profile and an ethylene octene copolymer thick bottom dielectric structure enable an improved electric field distribution. As a result, our quasi-vertical trench MOSFETs exhibit an avalanche breakdown voltage of 525 V and a positive temperature coefficient of 0.47 V/°C, in association with excellent on-state performance. In addition, temperature-dependent off-state characteristics of the trench MOSFETs are also analyzed in detail.