Analytical performance evaluation of AlGaN/GaN metal insulator semiconductor heterostructure field effect transistor and its comparison with conventional HFETs for high power microwave applications

In this work, a comprehensive analytical model for AlGaN/GaN MISHFET has been presented to evaluate the drain current characteristics, transconductance, and cut‐off frequency of the insulated device. The model takes into account polynomial dependence of sheet carrier density on position of quasi Fermi level to consider the quantum effects and to validate it from subthreshold to high conduction region. The effect of spontaneous and piezoelectric polarization at the AlGaN/GaN interface and parasitic source/drain resistances have also been incorporated in the analysis. Its advantages over conventional HFET structure are discussed in detail. For a MISHFET with quarter micron gate length, the cut‐off frequency is reported to be 52 GHz. The MISHFET shows remarkable 36% increase in drain saturation current. The model has a broad utility as it is equally applicable to HFETs as well. The present model is based on closed form expression and does not involve any fitting parameter. The results obtained are compared with experimental data and show excellent agreement, thereby proving the validity of the model.