Vertical Blocking Voltage Improvement of GaN HEMT Structures on n-SiC by Pre-Epitaxial Substrate Implantation

To overcome the use of expensive semi-insulating SiC substrates, we developed a method to increase the vertical blocking strength of n-SiC by argon implantation prior to the high temperature epitaxial growth (1150°C) of the (Al)GaN layers. We superimpose 4 argon implantation energies (30 keV + 60 keV + 180 keV + 360 keV) to a total maximal concentration of 1·1018 atoms/cm3 and observed a 90 V - 100 V increase of the vertical blocking strength by this method. Implantation profile and dose dependencies are studied showing that the results could be related to an increased substrate resistance achieved by implantation. HRXRD analysis shows that the defect density in the GaN buffer is not increased by substrate implantation.