Improved Dynamic RON of GaN Vertical Trench MOSFETs (OG-FETs) Using TMAH Wet Etch

This letter reports on the dynamic R_{\text{ON}} performance of large-area GaN vertical trench MOSFETs (OG-FETs) fabricated on bulk GaN substrates. OG-FETs demonstrated excellent DC performance with a breakdown voltage of 900 V and a R_{\text{ON}} of 4.1 \Omega (8.2 \text{m}\Omega \cdot \text {cm}^{2} ). However, damage to the trench sidewalls caused by RIE dry etching led to poor dynamic R_{\text{ON}} performance. An improved dynamic R_{\text{ON}} performance was achieved by following the RIE dry etch with a TMAH wet etch. With this process combination, the dynamic R_{\text{ON}} was reduced by more than 10 times compared with the dynamic R_{\text{ON}} in devices fabricated by dry etch only.