N-Polar GaN MIS-HEMTs on Sapphire With High Combination of Power Gain Cutoff Frequency and Three-Terminal Breakdown Voltage

Nitrogen polar SiN x /AlGaN/GaN/AlGaN metal– insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) with 28.6-nm equivalent GaN channel thickness grown by metal–organic chemical vapor deposition on sapphire substrate with a high combination of current/power gain cutoff frequencies ( $f_{T}/f_{\max }$ ) and three-terminal breakdown voltage (BV DS ) are demonstrated. $f_{T}$ /BV DS of 103 GHz/114 V and $f_{\max }$ /BV DS of 248 GHz/114 V were achieved in devices with the gate widths of $2 \times 50\mu \text{m}$ and $2 \times 25\mu \text{m}$ , respectively, comparing well with recent reports of fully passivated and vertically scaled Ga-polar GaN HEMTs. Devices with a gate width of $2 \times 75 \mu \text{m}$ showed the peak output power densities of 5.74 W/mm at 4 GHz and 6.29 W/mm at 10 GHz obtained by load-pull measurements.