High quality free-standing GaN substrates and their application to high breakdown voltage GaN p-n diodes

Recent development in GaN free-standing substrates have enabled fabrications of high performance vertical structure GaN devices. This letter reviews fabrication method of the high quality GaN substrates and reports increased breakdown voltages in vertical GaN p-n diodes fabricated on the substrates. By applying multiple lightly Si doped n-GaN drift layers to the p-n diode, record breakdown voltages (VB) of 4.7 kV combined with low specific differential on-resistance (Ron) of 1.7 mΩcm2 were achieved.