High-efficiency GaN HEMTs on 3-inch semi-insulating SiC substrates

We report on device performance and reliability of our 3" GaN high electron mobility transistor (HEMT) technology. AlGaN/GaN HEMT structures are grown on semi-insulating SiC substrates by metal-organic chemical vapor deposition (MOCVD) with sheet resistance uniformities better than 2%. Device fabrication is performed using standard processing techniques involving both e-beam and stepper lithography. AlGaN/GaN HEMTs demonstrate excellent high-voltage stability and large efficiencies. Devices with 0.5 mu m gate length exhibit two-terminal gate-drain breakdown voltages in excess of 160 V and drain currents well below 1 mA/mm when biased at 80 V drain bias under pinch-off conditions. Load-pull measurements at 2 GHz return both a linear relationship between drain bias voltage and output power as well as power added efficiencies beyond 55% up to 72 V drain bias for which an output power density of 9 W/mm with 25 dB linear gain is obtained. Reliability tests indicate a promising device stability under both radio frequency (R-F) and direct current (DC) stress conditions.