Hybrid Edge Termination for High-Voltage Vertical GaN Devices: Empirical Validation and Robust Processing Tolerance

This study presents empirical validation of a simulated novel hybrid edge termination (HET) structure with planar ion implantation processing for vertical gallium nitride (GaN) diodes. The hybrid structure combines a junction termination extension (JTE) with superimposed guard rings (GRs), creating zones with alternating implantation depths. A design optimization strategy is employed to match the charge profile in the termination to that of a reference beveled edge termination, and is validated through the fabrication of ~1.5 kV GaN diodes. The breakdown voltage of the hybrid termination is tied to the fitting error between the charge profile of the hybrid structure and the reference bevel, as confirmed through simulations and experimental results. The proposed structure successfully emulates the properties of a bevel termination without the need for complex etching or lithography procedures. Additionally, the tolerance of the proposed hybrid structure to major process variations during the wafer growth and device fabrication are studied in simulations. The hybrid termination structure showcases remarkable robustness against major process variations, making it a viable choice for high-yield manufacturing. The findings and patterns presented in this work offer significant insights for the design and large-scale production of forthcoming high-power vertical GaN devices.