Impact of parasitic resistances on the electrical characteristics of a SiC MESFET

The mathematical formulations of extrinsic resistances of a SiC-MESFET are developed and their impact on the electrical characteristics of the device has been studied in this work. Numerical techniques are used to calculate the drain current of a MESFET considering the existence of parasitic resistances. The analytical expressions of drain conductance, mutual conductance and cut off frequency of the device have been derived and their variations over different device parameters are studied incorporating the effect of extrinsic resistances. It is observed that the impact of parasitic resistances on the drain current and other parameters of the device is significant and device performance usually degrades with parasitic resistances. The parasitic resistances computed using our approach is compared with the experimentally extracted data reported earlier and a reasonably good agreement has been observed.