A vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage (BV). There is a discontinuity of the electric field at the interface of high-K and low-K layers due to the different dielectric constants of high-K and low-K dielectric layers. A new electric field peak is introduced in the n-type drift region of junction barrier Schottky diode (JBS), so the distribution of electric field in JBS becomes more uniform. At the same time, the effect of electric-power line concentration at the p-n junction interface is suppressed due to the effects of the high-K dielectric layer and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN JBS with a specific on-resistance (R on, sp ) of 2.07 mΩ·cm2 and a BV of 4171 V which is 167% higher than the breakdown voltage of the common structure, resulting in a high figure-of-merit (FOM) of 8.6 GW/cm2, and a low turn-on voltage of 0.6 V.

This paper proposes a vertical trapezoidal GaN p-n diode with a high-K/low-K compound dielectric (CD-TGD) to improve the breakdown voltage (BV). By introducing the compound dielectric structure, a new peak of electric field will be induced in the n-type GaN drift region of the trapezoidal diode, to make the electric field distribution in the drift-region more uniform. The key parameters of the CD-TGD, including the angle of the bevel structure, the doping concentration of drift region, and the size of high-K/low-K compound dielectric layers, have been comprehensively investigated by TCAD Silvaco simulation to reveal their impacts on the diode's properties. The breakdown voltage of the optimized structure is boosted from 2780 V for vertical GaN diodes (VGD) to 4360 V for CD-TGD, which is 56.8% higher than that of VGD. The on-state resistance of the optimized CD-TGD is 1.53 mΩ⋅cm 2 , yielding a high FOM of 12.4 GW/cm 2 . What is more, the average breakdown electric field is 2.73 MV/cm, which is much closer to the material limits of GaN. INTRODUCTIONAs silicon-based power device technology has approached its theoretical limit in terms of power density and power conversion efficiency, the development of alternative materials is now the focus of recent researches. Gallium nitride (GaN)-based power devices exhibit the superior performance required for next-generation high power and high frequency power electronics systems, because of their high breakdown strength, low onresistance and high switching speed [1][2][3].Recently, with the commercial availability of high-quality, free-standing GaN substrate, GaN-on-GaN devices have been used frequently, because of their higher breakdown voltage (BV), larger current capacity, and superior dynamic performance compared with their lateral counterparts [4][5][6][7][8][9]. Due to the electric field crowding around the periphery of the main junction which could cause premature breakdown, the BV of vertical power device is still difficult to reach that of the ideal parallel-plane device. Until now, Some junction termination techniques, such as floating limiting rings (FLRs) and field plate,This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.