Capacitance-voltage characteristics and cutoff frequency of pseudomorphic (AlGaAs/InGaAs) modulation-doped field-effect transistor for microwave and high-speed circuit applications

A two-dimensional analytical model for the capacitance-voltage characterist ics of a pseudomorphic AlGaAs/InGaAs modulation-doped field-effect transist or is developed using charge-control analysis for its microwave frequency a pplications. The model includes the effect of various fringing field capaci tances, and a cutoff frequency of 94.8 GHz is obtained for an L = 0.25 mu m device. The effect of traps has been included, which decreases the cutoff frequency. The results so obtained are compared with experimental data, and show excellent agreement, thereby proving the validity of the model. (C) 1 999 John Wiley & Sons, Inc.