Degradation Characteristics of Enhancement-Mode Gallium Nitride Cascoded FETs under different DC voltages

Depletion-mode gallium nitride (GaN) high-electron-mobility transistors (HEMTs) need to connect with an enhancement-mode silicon (Si) MOSFET for cascoded structures in order to achieve normally-off operation. The devices are submitted to electrical overstress to investigate the degradation phenomenon. The results demonstrate that degradation near the rated voltage of enhancement-mode GaN (e-GaN) Cascoded FETs can be a time-dependent process. There is no significant degradation of on-resistance and saturation current after a period of time for devices experienced 320V stress. The electrical characteristics of the devices are measured after 6 days of natural recovery. The on-resistance and saturation current of all devices exhibit reversibility, while the gate/source leakage current is irreversible.