I-V characteristics of GaAs MESFET with nonuniform doping profile

A simple analytical model of a GaAs MESFET with nonuniform doping is proposed. The analysis shows that at gate voltages well above the threshold (0.2-0.4 V) for a typical device the current saturation is related to the velocity saturation (with a possibility of a stationary domain formation at drain-to-source voltages high enough). Closer to the threshold the saturation is due to the channel pinchoff. In both regimes the nonuniformity of the doping profile may be essential. Another factor taken into consideration is the source series resistance which includes the contact resistance and the resistance of the gate-to-source region of the device. The calculated dependences of the transconductance and drain current on the gate voltage are in good agreement with the experimental results obtained by Eden, Zucca, Long, and others (1978).