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 24 GHz have been performed on a series of MBE-grown Mg-doped (10(17)-10(20-)cm(-3)) 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] > 3 x 10(18)cm(-3), 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 x 10(17)cm(-3) revealed the first evidence for the highly anisotropic g-tensor (g(parallel to)similar to 2.19, g(perpendicular to)similar to 0) expected for Mg shallow acceptors in wurtzite GaN. This result is attributed to the much reduced dislocation densities (<= 5 x 10(6) cm(-3)) and Mg impurity concentrations compared to those characteristic of the more conventional investigated Mg-doped GaN heteroepitaxial layers. Published by Elsevier B.V.