Optically detected magnetic resonance of (effective-mass) shallow acceptors in Si-doped GaN homoepitaxial layers

Optically detected magnetic resonance (ODMR) has been performed on Si-doped GaN homoepitaxial layers grown by organometallic chemical vapor deposition on free-standing GaN templates. In addition to intense excitonic bandedge emission with narrow linewidths (<0.4meV), these films exhibit strong shallow donor--shallow acceptor recombination at 3.27 eV. Most notably, ODMR on this photoluminescence band reveals a highly anisotropic resonance with g_∥=2.193±0.001 and g_⊥~0 as expected for effective-mass shallow acceptors in wurtzitic GaN from k{·}p theory. This previously elusive result is attributed to the much reduced dislocation density and impurity levels compared to those typically found in the widely investigated Mg-doped GaN heteroepitaxial layers. The possible chemical origin of the shallow acceptors in these homoepitaxial films will be discussed.