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

AlN/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 AlN/GaN MISFETs and Al
32
Ga
68
N/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 HFETs. First results from fabricated AlN/GaN devices with 1.1 μm gate length and 200 μm gate width showed a maximum drain current density of ∼470 mA/mm and a peak extrinsic transconductance of 80 mS/mm. Sparameter 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 AlN/GaN MISFETs addressing their physical modeling and experimental highfrequency characteristics.