Simulation Study of p-GaN HEMT with Gate Floating Metal Rings

In this paper, the effect of GFMR on the gate breakdown voltage is investigated by Silvaco simulated software. The gate breakdown voltage increases from 7 V to 16.1 V by adopting GFMR structure, which is attributed to more uniform distribution of the electric field. The GFMR introduces a new electric field peak, and reduces the main peak value, thus improving breakdown voltage. However, the GFMR cannot give full play to the ability to disperse electric field, due to heavily-doped in the p-GaN layer. The heavily- doped will limit the depletion region expanding and concentrated electric field. Therefore, the lightly-doped and heavily-doped stacking p-GaN layer is proposed to optimize GFMR structure. The lightly-doped layer makes the depletion region easy to expand, and heavily-doped layer ensures the realization of enhancement devices. The results show that the gate breakdown voltage can achieve 23.8 V, 3 times higher than conventional p-GaN HEMT.