Analysis of lags and current collapse in field-plate AlGaN/GaN HEMTs with deep acceptors in a buffer layer

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 insulator thickness under the field plate is also studied, suggesting that there is an optimum thickness of insulator to minimize the current collapse of AlGaN/GaN HEMTs.