Analytical model for dc characteristics and small-signal parameters of AIGaN/GaN modulation-doped field-effect transistor for microwave circuit applications

An improved charge-control model for the dc and microwave characteristics of an Al0.15Ga0.85N/GaN modulation-doped FET (MODFET) is developed. The effect of piezoelectric polarization-induced charge at the AlGaN/GaN heterointerface has been incorporated. The small-signal microwave parameters have been evaluated to determine the current–gain cutoff frequency (ft). High current levels (503.4 mA/mm), large gm (160 mS/mm), and high ft (9.48 GHz) are achieved for a 1 μm Al0.15Ga0.85N/GaN MODFET. The results so obtained are in close agreement with experimental data.