1.7kV fully-vertical GaN trench MOSFET with nitrogen ion-implanted guard rings

This work presents a high-performance fully vertical GaN trench MOSFET on GaN substrate, featuring a selective nitrogen ion-implanted guard rings edge termination. The device exhibits a high breakdown voltage of 1715 V, a normally-off operation with a threshold voltage (V_th) of 4.1 V, and a specific on-resistance (R_on,sp) of 5.3 mΩ cm²and 262 Ω∙mm, respectively. The termination relies on a single-mask selective implantation process, where multi-energy nitrogen implantation creates semi-insulating regions in the GaN layer, yielding electrically isolated floating p-GaN rings. This method capitalizes on the inherent features of the material layer structure to implement the termination, without the need of complex processing steps. Technology computer-aided design simulations show that the uniformly formed p-GaN rings effectively redistribute the electric field, mitigating peak field crowding at the device periphery. With a 5-ring design, the device demonstrates excellent voltage-blocking capability. The proposed implantation-based guard-ring technique, notable for its process efficiency and fabrication simplicity, provides a reliable approach for realizing high-performance 1.7 kV-class vertical GaN trench MOSFETs.