V-Gate GaN HEMTs for X-Band Power Applications

GaN high electron mobility transistors (HEMTs) with novel V-shaped gates were developed. The V-gate GaN HEMTs feature two key technologies: One is the use of an epitaxially grown GaN cap layer to isolate the surface charging from affecting the 2DEG channel; the other one is the adoption of a V-shaped gate-recess geometry that effectively mitigates the electric-field crowding at the gate edge. The combination of these two technologies enables high-voltage and dispersion-free operation without significantly sacrificing the devices' bandwidth. At 10-GHz frequency and 48-V drain bias, the V-gate devices exhibited an output power density of 12.2 W/mm with the associated power added efficiency as high as 65%. This result represents, to date, the highest reported efficiency at this frequency and operating voltage, indicating that the V-gate GaN HEMTs are suitable for X-band power applications.