650-V E-Mode GaN Tri-Gate MIS-HEMTs With Gate-Buffer Coupled Structure to Suppress Substrate-Induced Crosstalk

This work presents a comprehensive study of the substrate-induced crosstalk effect in the tri-gate MIS-HEMT with gate-buffer coupled structure. Employing the standard low-resistivity Si substrate, the GaN-on-Si power IC platform is successfully elevated to 650 V level. In the proposed device, the gate is deeply recessed into the GaN buffer region, forming an extended electrostatic boundary condition that effectively reshapes the substrate-originated electric-field distribution. Consequently, the device exhibits exceptional stability, with a threshold voltage shift of +0.2 V/-0.3 V under a full -650 V/+650 VVSUBswing, and maintains robust dynamic switching characteristics. These results demonstrate the strong potential of the proposed tri-gate MIS platform for high-voltage monolithic GaN power ICs on silicon substrates.