Optical detection of electron paramagnetic resonance in low-dislocation-content GaN grown by hydride vapor-phase epitaxy

Abstract

Three broad overlapping photoluminescence bands, centered at $\ensuremath{\sim}1.75 \mathrm{eV}$ (red), $\ensuremath{\sim}2.2 \mathrm{eV}$ (yellow), and $\ensuremath{\sim}2.33 \mathrm{eV}$ (green), are observed in low-dislocation-content GaN grown by the hydride vapor-phase epitaxy method. Optical detection of electron paramagnetic resonance (ODEPR) studies reveal that each is fed by a spin-dependent electron transfer from a shallow donor to a deeper defect, which is different for each of the bands, and different from defects previously found in GaN grown by the more conventional epitaxy methods (metal-organic vapor-phase epitaxy and molecular beam epitaxy). The g-value progression for the deeper defects suggests a two-stage luminescence process in which the luminescence arises from hole capture at the specific defect in each case, after the spin-dependent electron capture process observed by ODEPR. This model also fits for the deep level usually found in the yellow band for more heavily dislocated materials, as originally suggested by Glaser. An additional weak anisotropic ODEPR signal is also observed in the red and yellow bands. None of the signals show resolved hyperfine interactions, and their chemical and/or lattice structures remain unknown.