Herein, we propose and demonstrate the edge termination for GaN-based one-sided abrupt p–n junctions. The structure is comprised of a combination of a shallow negative bevel mesa and selective-area p-type doping under the mesa. Based on the Technology Computer Aided Design (TCAD) simulation, the maximum electric field at the junction edge is markedly reduced to approximately 1.3 times that of the parallel-plane electric field in the proposed structure, which is almost half of the unimplanted diode. The TCAD simulation also shows that the shallow mesa angle of 6° effectively reduces the optimum acceptor concentration (Na) in the implanted region and enhances the breakdown voltage. The optimum Na value can be covered by the proposed technology based on the Mg-ion implantation and subsequent ultra-high-pressure annealing (UHPA). Using the formation of the shallow bevel mesa, the Mg-ion implantation, and the UHPA process, we experimentally demonstrate the p–n diodes with a breakdown voltage over 600 V, which is in good agreement with the TCAD simulation. The proposed method can be applied to a vertical trench-gate metal-oxide-semiconductor field-effect transistor with a high figure-of-merit.

A nearly-ideal edge termination for GaN p-n junctions was designed and demonstrated using Mg-ions implanted field limiting rings (FLRs). The FLRs were fabricated via the ultra-high-pressure annealing process after implanting Mg-ions into the etched n-type region outside the main p-n junction. The results of the technology computer-aided design simulation indicate that by optimizing the space and width of the rings, the breakdown voltage (BV) can be increased by over 90% of the ideal parallel plane BV (973 V). Accordingly, the fabricated diodes exhibited low leakage current and a BV of 897 V (92% of the ideal BV).

The electrical properties of vertical GaN trench MOSFETs without drift layers were evaluated to investigate the effect of nitrogen plasma treatment on the trench sidewalls. It is demonstrated that nitrogen plasma treatment improves the channel property of the vertical GaN trench MOSFET. The possible mechanism of this improvement is the supply of nitrogen atoms from nitrogen plasma treatment to the trench surfaces, and the compensation of the nitrogen vacancies near the trench surfaces by the nitrogen atoms during gate oxide annealing. The temperature dependence and the limiting factors of the channel property are also discussed.

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