AlGaN/GaN/GaN:C Back-Barrier HFETs With Breakdown Voltage of Over 1 kV and Low $R_{\scriptscriptstyle {\rm ON}} \times A$

A systematic study of GaN-based heterostructure field-effect transistors with an insulating carbon-doped GaN back barrier for high-voltage operation is presented. The impact of variations of carbon doping concentration, GaN channel thickness, and substrates is evaluated. Tradeoff considerations in on-state resistance versus current collapse are addressed. Suppression of the off-state subthreshold drain-leakage currents enables a breakdown voltage enhancement of over 1000 V with a low on-state resistance. Devices with a 5-μm gate-drain separation on semi-insulating SiC and a 7-μm gate-drain separation on n-SiC exhibit 938 V and 0.39 mΩ·cm² and 942 V and 0.39 m Ω·cmcm², respectively. A power device figure of merit of ~ 2.3 × 10⁹ V²/Ω·cm² was calculated for these devices.