AlGaN∕GaN HEMTs on silicon substrates with fT of 32∕20 GHz and fmax of 27∕22 GHz for 0.5∕0.7 m gate length

Abstract

AlGaN/GaN HEMTs on silicon substrates have been realised and their static and small signal characteristics investigated. The AlGaN/GaN (x=0.23) material structures were grown on (111) p-Si by LP-MOVPE. Devices exhibit a saturation current density of 0.53 to 0.68 A/mm and a peak extrinsic transconductance of 110 mS/mm. A unity gain frequency of 20 and 32 GHz and a maximum frequency of oscillation of 22 and 27 GHz are obtained for devices with a gate length of 0.7 and 0.5 µm, respectively. These values are the highest reported so far on AlGaN/GaN/Si HEMTs and are comparable to those known for devices using sapphire and SiC substrates.