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 (<0.4 meV), 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{sub {parallel}} = 2.193 {+-} 0.001 and g{sub {perpendicular}} {approx}0 as expected for effective-mass shallow acceptors in wurtzitic GaN from k {center_dot} 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.