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 (fT) and maximum oscillation frequency (fmax) 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 VDS=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.