Modeling of source/drain access resistances and their temperature dependence in GaN HEMTs

In this paper, we present the modeling of source/drain access resistances in the surface potential based model named “Advanced SPICE Model for High Electron Mobility Transistor” (ASM-HEMT) for AlGaN/GaN HEMTs. From TCAD simulation, it is shown that nonlinear source and drain resistances increase with drain current which is due to the saturation of electron velocity in this region. Accurate modeling of this access resistance is of immense importance to correctly predict the drain current, transconductance (g
_m
) and hence the transit frequency (f
_T
) at higher current. The model shows excellent agreement with experimental data at room temperature. Variation of measured ON-resistance (R
_on
) with temperature is well predicted by model which justifies the accuracy of temperature dependence model of source/drain resistances.