AlGaN/GaN HEMTs on resistive Si (111) substrate grown by gas-source MBE

Al0.3Ga0.7/GaN high electron mobility transistor (HEMT) structures have been grown on resistive Si(111) substrate by molecular beam epitaxy (MBE) using ammonia (NH3). The use of an AIN/GaN intermediate layer allows a resistive buffer layer to be obtained. High sheet carrier density and high electron mobility arc obtained in the channel. A device with 0.5 mum gate length has been realised exhibiting a maximum extrinsic transconductance of 160 ms/mm and drain-source current exceeding 600 mA/mm. Small-signal measurements show f(t) of 17 GHz and f(max) of 40 GHz.