Quasi-vertical GaN SBD device structure and parameter optimization

To ensure a high reverse breakdown voltage at a small size and improve the uniform electric field of the terminal structure of the device. This paper is based on simulation calculations to optimize the vertical power devices. Establish a model of GaN vertical SBD, N-GaN drift layer thickness is 4μm-5μm, the doping concentration is 1.5×1016cm-3. N+GaN the doping concentration of the current extension layer is 1019cm-3. Under the premise of determining the thickness of the current expansion layer as 5μm, this paper sets the thickness of current expansion layer (Ln+gan1) as 0.1μm，sets the thickness of N+GaN (Ln+gan) as 0.6μm. Then sets Lac1 and Lac2 optimized as 10μm and 5μm. The on-resistance of the optimized quasi-vertical SBD reduce from 0.93 mΩ•cm2 to 0.55 mΩ•cm2, breakdown voltage increase from 530V to 560V. Secondly this paper optimized the terminal structure of the device, determine the passivation layer thickness as 0.4μm, the length of field plate is 8μm. Finally, the influence of the two terminal structures on the device is compared, the field plate has no effect on the forward characteristics of the device. After optimization, the on-resistance is 0.565mΩ•cm2, increases the breakdown voltage of the device to 632V.