Impact of Trench Dimensions on the Device Performance of GaN Vertical Trench MOSFETs

In this letter, we have examined the impact of trench dimensions on the breakdown voltage and ON-resistance of trench MOSFETs fabricated on sapphire and bulk GaN substrates. Contrary to simulation studies, the breakdown voltage decreased with an increase in trench dimensions in devices fabricated on sapphire substrates. However, such breakdown voltage dependence with trench dimensions was not observed in devices fabricated on bulk GaN substrates of the same area. The observed trend on GaN on sapphire devices was associated with the equivalently reduced number of dislocations per device area. These results give an insight into how dislocations could affect breakdown voltage in power MOSFETs.