Reduction of buffer-related current collapse in GaN FETs under favour of a field plate

Two-dimensional transient analysis of GaN MESFETs with a semi-insulating buffer layer is performed in which a deep donor and a deep acceptor are considered in the buffer layer, and the results are compared between the two cases with and without a field plate. It is shown that buffer-related drain lag is reduced by introducing a field plate because trapping effects become smaller. It is also shown that current collapse and gate lag are also reduced in the field-plate structure. The dependence on SiN passivation layer thickness is also studied, indicating that there is an optimum SiN thickness to minimize the buffer-related current collapse and drain lag in GaN-based FETs.