A uniform, reproducible and reliable GaN HEMT technology with breakdown voltages in excess of 160 V delivering more than 60% PAE at 80 V
We report on device performance and reliability of our 3" GaN HEMT technology. AlGaN/GaN HEMT structures are grown on semi-insulating SiC substrates by MOCVD with sheet resistance uniformities better than 3%. Device fabrication is performed using standard processing techniques involving both e-beam and stepper lithography. The process technology exhibits an excellent uniformity across a single wafer as well as high reproducibility between individual wafers of the same or a different batch. Loadpull mapping of 8x400 µm gate periphery devices with 0.5 µm gate length across all 21 cells on entire 3-inch wafers yields a PAE of (60±2)% with only 2% scatter of the mean PAE from wafer to wafer. AlGaN/GaN HEMT's demonstrate superior high-voltage stability and large efficiencies. Devices with 0.5 µm 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 60% up to 80 V drain bias. At 88 V an output power density of 15 W/mm with 24 dB linear gain is obtained. Reliability tests indicate a promising device stability under both radio frequency (RF) and direct current (DC) stress conditions.