545-mA/mm E-mode Recessed-Gate GaN MOSHEMT (Vth > 4V) by Ion Beam Etching

Normally-off recessed-gate AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs) were fabricated using argon-based ion beam etching and thoroughly characterized. By partially recessing the AlGaN barrier, the device achieved a threshold voltage of 4.22 V, saturation drain current of 545 mA/mm, and small on-resistance of 3.63 Ω·mm at a gate bias of 8 V. The recessed-gate MOSHEMT demonstrated good breakdown characteristics that by scaling the gate-to-drain distance (
L_gd
) from 2 μm to 10 μm, breakdown voltages were steadily enhanced from 202 V to 730 V. The device exhibited good dynamic performance that with an off-state drain stressing of 100 V, low current collapse of 14.1% was obtained. After applying a -10 V gate stressing for a duration of 100 s, the threshold voltage was only negatively shifted by 0.40 V. Overall, Baliga’s figure-of-merit (FOM) of 567 MW/cm
²
has been achieved for MOSHEMTs with
L
_gd
of 10 μm, indicating ion beam etching paves a promising path for enhancement-mode recessed-gate MOSHEMT fabrication.