Compact Model of Current Collapse in Heterostructure Field-Effect Transistors

In this paper, compact analytical model for the heterostructure field-effect transistor (HFET) current-voltage (I-V) characteristics, accounting for the large-signal dispersion, also referred to as current collapse, is presented. The model is based upon an experimentally established fact that the dispersion is mainly due to carrier trapping at the source and drain sides of the gate edges. In wide-bandgap heterostructures like AlGaN/GaN, the characteristic trapping-generation times are several orders of magnitude longer than the signal period at typical operating frequencies. Thus, the radio frequency signal "sees" an averaged I-V characteristic resulting from carrier trapping-generation. The approach, based on this difference, leads to a compact quasi-steady-state analytical model of the HFET I -V characteristics that can be easily implemented in device-circuit simulators. The model shows close agreement with the experimental data