Optimization of high breakdown voltage vertical trapezoidal GaN p‐n diode with a high‐K/low‐K compound dielectric for power applications

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·cm2, yielding a high FOM of 12.4 GW/cm2. What is more, the average breakdown electric field is 2.73 MV/cm, which is much closer to the material limits of GaN.