Over 2 A Operation at 250 °C of GaN Metal–Oxide–Semiconductor Field Effect Transistors on Sapphire Substrates

We investigated normally off operation GaN metal–oxide–semiconductor field effect transistors (MOSFETs). The drain current of GaN MOSFETs with a gate width of 1 mm increased from 0.004 to 0.1 A by which the channel length decreased from 100 to 2 µm. However, the on-resistance was increased by shortening a channel length. In addition, the drain current of GaN MOSFETs with the channel length of 4 µm was increased from 0.08 A to more than 2.2 A, by which the channel width was increased from 1 to 16 mm. As a result, we achieved normally off operation GaN MOSFETs with the highest operation temperature of 250 °C. The drain current was 2.2 A at V g =+14 V. The threshold voltage ( V th ) was +3 V.