Simulation of lags and current collapse in field-plate AlGaN/GaN HEMTs with different types of buffer layers

We make 2-D transient simulations of field-plate AlGaN/GaN HEMTs with a semi-insulating buffer layer, where a deep acceptor above the midgap is considered. It is studied how the deep acceptor and the field plate affect lag phenomena and current collapse. It is shown that the drain lag and current collapse could be reduced by introducing a field plate, as in a case with a deep acceptor compensated by a deep donor in the buffer layer. This reduction occurs because electron trapping by the deep acceptors is weakened by the field plate. The dependence on the fieldplate length and the insulator thickness under the field plate is also studied, showing that the rates of lags and current collapse are quantitatively similar between the two cases with different types of buffer layers when the deep-acceptor density in the buffer layer is the same.