Optical and magnetic resonance studies of Mg-doped GaN homoepitaxial layers grown by molecular beam epitaxy

Low-temperature photoluminescence (PL) and optically detected magnetic resonance (ODMR) at 24GHz have been performed on a series of MBE-grown Mg-doped (1017–1020 cm3) GaN homoepitaxial layers. High-resolution PL at 5K revealed intense bandedge emission with narrow linewidths (0.2–0.4meV) attributed to annihilation of excitons bound to shallow Mg acceptors. In contrast to many previous reports for GaN heteroepitaxial layers doped with [Mg]43 1018 cm3, the only visible PL observed was strong shallow donor–shallow acceptor recombination with zero phonon line at 3.27 eV. Most notably, ODMR on this emission from a sample doped with [Mg] of 1 1017 cm3 revealed the first evidence for the highly anisotropic g-tensor (gJ2.19, g?0) expected for Mg shallow acceptors in wurtzite GaN. This result is attributed to the much reduced dislocation densities (p5 106 cm3) and Mg impurity concentrations compared to those characteristic of the more conventional investigated Mg-doped GaN heteroepitaxial layers. Published by Elsevier B.V