Electrical and Recombination Properties of Polar Orthorhombic kappa-Ga2O3 Films Prepared by Halide Vapor Phase Epitaxy

In this study, the structural and electrical properties of orthorhombic kappa-Ga2O3 films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For kappa-Ga2O3/AlN/Si structures, the formation of two-dimensional hole layers in the Ga2O3 was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of kappa-Ga2O3 and AlN. Structural studies indicated that in the thickest kappa-Ga2O3/GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 mu m and 86 mu m) kappa-Ga2O3 films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 mu m layer of the grown films contains a high density of rather deep electron traps near E-c - 0.3 eV and E-c - 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in kappa-Ga2O3. The film with the greatest thickness of 86 mu m was irradiated with protons and the carrier removal rate was about 10 cm(-1), which is considerably lower than that for beta-Ga2O3.