AlN/GaN MISFET for high frequency applications: Physical simulation and experimental evaluation

AIN/GaN metal insulator semiconductor field effect transistors (MISFETs) were designed, simulated and fabricated. DC and S-parameter measurements were also performed. Drift-diffusion simulations using DESSIS compared AIN/GaN MISFETs and A₃₂Ga₆₈N/GaN Heterostructure FETs (HFETs) with the same geometries. The simulation results show the advantages of AIN/GaN MISFETs in terms of higher saturation current, lower gate leakage and higher transconductance than AlGaN HFETs. First results from fabricated AIN/GaN devices with 1.1 mum gate length and 200 mum gate width showed a maximum drain current density of ~-470 mA/mm and a peak extrinsic transconductance of 80 mS/mm. S-parameter measurements showed that the current-gain cutoff frequency (f_T) and maximum oscillation frequency (f_max) were 2.8 GHz and 10.3 GHz, respectively. To the authors knowledge this is the first report of a systematic study of AIN/GaN MISFETs addressing their physical modeling and experimental high-frequency characteristics.