Reduction of buffer-related current collapse in field-plate AlGaN/GaN HEMTs

Two-dimensional transient analyses of field-plate AlGaN/GaN HEMTs are performed in which a deep donor and a deep acceptor are considered in a semi-insulating buffer layer, and quasi-pulsed current-voltage curves are derived from them. It is studied how the existence of field plate affects buffer-related drain lag, gate lag and current collapse. It is shown that the drain lag is reduced by introducing a field plate, because electron injection into the buffer layer is weakened by it, and the trapping effects are reduced. It is also shown that the current collapse and gate lag are reduced in the field-plate structure. The dependence on SiN passivation layer thickness is also studied, suggesting that there is an optimum thickness of SiN layer to minimize the buffer-related current collapse and drain lag in AlGaN/GaN HEMTs.