Y. Saito, R. Tsurumaki, N. Noda, K. Horio
Shibaura institute of Technology,
Keywords: GaN, HEMT, buffer layer, current collapse, field plate
Summary:We make a two-dimensional transient analysis 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 density and the field plate affect buffer-related lag phenomena and current collapse. It is shown that the introduction of field plate is effective to reduce the lags and current collapse. It is also shown that without a field plate the drain lag and current collapse increase with increasing the deep-acceptor density as expected because the deep acceptors act as electron traps, But with a field plate, surprisingly, the lags and current collapse are shown to be smaller when the deep-acceptor density becomes higher. This indicates that the field plate on the device surface is effective to reduce the buffer-related current collapse when the acceptor density in the buffer layer is high and electrons are not so diffused into the buffer layer.