Contact engineering of GaN-on-silicon power devices for breakdown voltage enhancement

Two contact engineering approaches are proposed and investigated to enhance the breakdown voltage V BK in GaN-on-Si power devices, including the hybrid Schottky–ohmic-drain structure for AlGaN/GaN HEMTs and the selective Si-diffusion structure for AlGaN/GaN SBDs. With the hybrid Schottky–ohmic drain, the devices showed a zero onset voltage and reduced off-state leakage current by one order of magnitude, compared with that of the traditional ohmic-drain devices. The breakdown voltage was also enhanced with comparable on-resistance. For the SBDs with the selective silicon-diffusion layer underneath ohmic metal at the cathode, a low-contact resistance R c of 0.2 Ω mm and a smooth ohmic metal morphology were obtained. The SBDs with the additional silicon diffusion layer showed enhanced V BK , compared with that of the conventional SBDs. The results demonstrate that the proposed contact engineering approaches are useful for the breakdown voltage enhancement of GaN-on-Si power devices.