Point defect localization and cathodoluminescence emission in undoped ϵ-Ga2O3

In this study, experimental and theoretical investigations have been performed on nominally undoped ϵ-Ga2O3 films deposited on (0001)-Al2O3 substrates by metal-organic vapor phase epitaxy using different O and Ga precursor ratios. Hydrogen and helium were used as carrier gas. Low-temperature cathodoluminescence (CL) broad emissions extending over the range 1.5-3.4 eV were deconvoluted in five peaks, whose position, integrated intensity, and full width at half maximum were investigated in the temperatures range 80 K-300 K. A non-monotonic behavior of the extracted CL peaks is observed, which is attributed to localization phenomena connected with families of point defects. The behavior of two main luminescence emissions with temperature has been simulated using the localized state ensemble model. The derived parameters agree with the experimental observations and provide a new interpretation of micro-and macroscale disorder inside ϵ-Ga2O3 and related potential fluctuations.