High power hybrid and MMIC amplifiers using wide-bandgap semiconductor devices on semi-insulating SiC substrates

An overview of hybrid and monolithic high-power microwave amplifiers using SiC MESFET and GaN HEMT active devices is presented. High power densities of 5.2 W/mm and 63% power added efficiency (PAE) have been demonstrated for SiC MESFETs at 3.5 GHz. This performance has driven the development of wide-bandwidth MMIC amplifiers, which have yielded 37 W of pulsed power at 3.5 GHz. GaN HEMTs on SiC substrates can achieve these high performance levels at frequencies where SiC cannot operate. At 10 GHz, a 12-mm GaN HEMT hybrid amplifier achieved a CW output power level of 38 W with an associated gain of 8 dB and PAE of 29%, complementing a previous pulsed result of 50.1 W. MMIC amplifiers have also been demonstrated using GaN-on-SiC technology. At 16 GHz, a two-stage GaN HEMT MMIC wide-bandwidth amplifier was capable of a peak power level of 24.2 watts with an associated gain of 12.8 dB and PAE of 22%. Recently, a 6-mm single-stage narrow-band MMIC amplifier has produced 32 watts of pulsed power at 10 GHz with an associated gain of 8.3 dB and a PAE of 35.3%. Finally, to validate progress in scaling unit cell performance to large devices, we have demonstrated 103 W of CW power from a single GaN HEMT transistor at 2 GHz with an associated drain efficiency of 52%.