AlGaN/GaN HFETs fabricated from maskless selectively grown mesas on Si(111) substrates
AlGaN/GaN heterostructure field effect transistors (HFETs) fabricated from maskless selectively grown mesas by ammonia molecular beam epitaxy on Si(111) substrates are demonstrated. With 0.8 µm gate length, the devices exhibited maximum drain current and transconductance of 425 mA/mm and 140 mS/mm, respectively. Values of fT and fMAX of 8 and 19 GHz, respectively, were obtained from RF measurements. A 50 nm-thick SiNx passivation layer was found to be very effective in mitigating the current collapse.