Improved Dynamic R ON 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.