HVPE Growth and Characterization of Thick kappa-Ga2O3 layers on GaN/Sapphire Templates

Ga2O3 layers with thickness from 10 to 86 mu m were grown by halide vapor phase epitaxy (HVPE) on GaN(0001)/sapphire templates in a hot wall reactor at 570 degrees C, with the growth rate of about 3-4 mu m h(-1). The grown layers consisted of pure (001)-oriented kappa-Ga2O3 polymorph with no admixture of beta-Ga2O3 or alpha-Ga2O3 phases. The narrowest (004) X-ray rocking curves were observed for 13-20 mu m thick kappa-Ga2O3 layers. A further increase in thickness results in deterioration of the crystal quality which is indicated by the broadening of rocking curves. Electrical measurements of the thick layers revealed that they were n-type, with the concentration of shallow donors gradually decreasing from similar to 10(16 )cm(-3) to similar to 10(15 )cm(-3). Deep level transient spectroscopy (DLTS) measurements revealed the presence of deep traps with levels near E-c-0.3 eV, E-c-0.6 eV, E-c-0.7 eV, E-c-0.8 eV, E-c-1 eV, with the E-c-0.8 eV being predominant.