Study of the effect of circular p-GaN gate on the DC characteristics of AlGaN/GaN HEMTs

In this paper, we use Silvaco-ATLAS two-dimensional numerical simulation to calculate the performance of two different circular-gate AlGaN/GaN HEMT device models. The influence of the special circular-gate structure on the DC characteristics of the AlGaN/GaN HEMT device is studied and compared with that of conventional devices. Compared with conventional, the threshold voltage of the drain-center and source-center circular-gate devices increased from 1.1 V to 1.5 V, while the transconductance improved from 245 mS mm-1 to 328 mS mm-1 and 285 mS mm-1 respectively. In the on-state of devices, the maximum saturation output current increased from 536 mA mm-1 to 620 mA mm-1 and 650 mA mm-1 . Furthermore, the breakdown voltage of the source-center circular-gate device rose from 765 V to 870 V compared to conventional devices; however, for the drain-center circular-gate device it was only at 685 V due to concentrated electric fields outside the drain region-this limitation can be effectively addressed by increasing the drain area. Simulation results demonstrate that circular-gate AlGaN/GaN HEMT devices can avoid edge effects, improve electric field distribution, and alleviate self-heating effects.