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

Abstract

Abstract 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.

Keywords

• Optimisation techniques
• Junction and barrier diodes