High-Performance N-Face GaN Microwave MIS-HEMTs With > 70% Power-Added Efficiency

A high-performance N-face GaN metal-insulator-semiconductor high-electron-mobility transistor was fabricated. A dual-AlN back-barrier scheme was developed using polarization engineering to provide a large total dipole moment, which allowed enhanced modulation doping for a higher 2-D electron gas density without parallel conduction. Devices with 0.6-mum gate length showed an
fT
and
f

_max
of 17 and 58 GHz, respectively. A highest power-added efficiency (PAE) of 71% at 4 GHz was measured in these devices with 20-V drain bias. At 28 V, an output power density of 6.4 W/mm with 67% PAE was achieved.