1.7 kV normally-off p-GaN gate high-electron-mobility transistors on a semi-insulating SiC substrate

A study of 1.7 kV normally-off p-GaN gate high-electron-mobility transistors (HEMTs) on SiC substrates is presented. The fabricated p-GaN HEMT with a gate-drain spacing L-GD = 5 mu m exhibited a threshold voltage of 1.10 V, a maximum drain current of 235 mA/mm, an ON/OFF ratio of 10(8), and a breakdown voltage of 440 V. Benefiting from the semi-insulating and high-critical-electric-field substrate, the p-GaN HEMT with L-GD = 23 mu m achieved the remarkably high breakdown voltage of 1740 V with substrate grounded. This breakdown voltage is very high compared with the reported values for p-GaN HEMTs on silicon substrates with substrate grounded. The vertical breakdown voltage for the p-GaN-on-SiC material exceeded 3 kV with substrate grounded. In addition, the maximum drain current at 500 K was 48% of that at 300 K with a negligible threshold voltage shift. These results indicate the substantial potential of p-GaN gate HEMTs on SiC substrates for high-voltage power applications.