Analysis of Reduction in Lag Phenomena and Current Collapse in Field-Plate AlGaN/GaN HEMTs With High Acceptor Density in a Buffer Layer

We make a 2-D transient analysis of field-plate AlGaN/GaN HEMTs with a semi-insulating buffer layer, where only a deep acceptor above the midgap is considered. The deep-acceptor density is varied between 10¹⁷ cm^-3and 8 × 10^-17 cm^-3. It is studied how the deep-acceptor density and the field plate affect the buffer-related drain lag and gate lag, and current collapse. It is shown that the lags and current collapse are reduced by introducing a field plate. This reduction occurs because electron trapping by the deep acceptors is weakened by the field plate. It is also shown that without a field plate, the drain lag and current collapse increase with increasing the deep-acceptor density as expected, although the gate lag decreases when the deep-acceptor density becomes high in the region between 2 × 10¹⁷ cm^-3 and 8 × 10¹⁷ cm^-3. On the other hand, with a field plate, surprisingly, the lags and current collapse decrease when the deep-acceptor density becomes high. This is attributed to the fact that the reduction in drain lag and current collapse by introducing a field plate becomes more significant when the deep-acceptor density becomes higher.