High power demonstration at 10 GHz with GaN-AlGaN HEMT hybrid amplifiers

The GaN/AlGaN-on-SiC HEMT is being pursued as an RF power device on which to base next generation X-band and K-band power amplifiers. Previous demonstrations of extremely high power density and total RF power from GaN/AlGaN HEMTs on SI SiC substrates (Sheppard et al., 1999; Wu et al., 1999) adequately demonstrate their potential for improved performance over GaAs-based devices. Considering the recent advances in III-nitride growth and processing techniques, it is not surprising that GaN/AlGaN HEMTs on SiC substrates are beginning to the reach the extremely high power levels that have been predicted for this material system. To continue this trend, we are pursuing high quality HEMT structures with 15% AlGaN molar fraction (MF) in order to fabricate large area devices and demonstrate high power levels. We report the demonstration of over 40 W from a single GaN/AlGaN transistor at 10 GHz under pulsed mode conditions. This high power demonstration includes the first implementation of SiC substrate vias on a GaN-on-SiC microwave transistor for improved gain at X-band.