Recessed-Gate Enhancement-Mode GaN MOSFETs With a Double-Insulator Gate Providing 10-MHz Switching Operation

Recessed-gate GaN metal-oxide-semiconductor field-effect transistors with a double-insulator gate configuration demonstrate 10-MHz switching operation of which delay time is <35 ns. The recess structure is fabricated by etching the Al0.19Ga0.81N layers to expose their underlying AlN layers. The devices include a thermally oxidized AlN layer onto which an Al2O3 film is formed by atomic layer deposition, which works as a gate insulator. This structure performs enhancement-mode operation with a typical threshold voltage of 1.4 V. A maximum drain current of 158.3 mA/mm is achieved at 6 V gate bias and maximum transconductance is 52.1 mS/mm at 10 V drain bias.