AlN/GaN Metal Insulator Semiconductor Field Effect Transistor on Sapphire Substrate

Abstract

AlN/GaN Metal Insulator Semiconductor Field Effect Transistors (MISFETs) were designed, simulated and fabricated. DC, S-parameter and power measurements were also performed. Drift-diffusion simulations using DESSIS compared AlN/GaN MISFETs and Al₃₂Ga₆₈N/GaN Heterostructure FETs (HFETs) with the same geometries. The simulation results show the advantages of AlN/GaN MISFETs in terms of higher saturation current, lower gate leakage and higher transconductance than AlGaN/GaN HFETs. First results from fabricated AlN/GaN devices with 1μm gate length and 200μm gate width showed a maximum drain current density of ∼380mA/mm and a peak extrinsic transconductance of 85mS/mm. S-parameter measurements showed that currentgain cutoff frequency (f_T) and maximum oscillation frequency (f_max) were 5.85GHz and 10.57GHz, respectively. Power characteristics were measured at 2GHz and showed output power density of 850mW/mm with 23.8% PAE at V_DS=15V. To the authors knowledge this is the first report of a systematic study of AlN/GaN MISFETs addressing their physical modeling and experimental high-frequency characteristics including the power performance.