Photoluminescence of Mg-doped m-plane GaN grown by MOCVD on bulk GaN substrates

Photoluminescence (PL) properties are reported for a set of m-plane GaN films with Mg doping varied from mid 10 18 cm -3 to well above 10 19 cm -3 . The samples were grown with MOCVD at reduced pressure on low defect density m-plane bulk GaN templates. The sharp line near bandgap bound exciton (BE) spectra observed below 50 K, as well as the broader donor-acceptor pair (DAP) PL bands at 2.9 eV to 3.3 eV give evidence of several Mg related acceptors, similar to the case of c-plane GaN. The dependence of the low temperature BE spectra on excitation intensity as well as the transient decay behavior demonstrate acoustic phonon assisted transfer between the acceptor BE states. The lower energy donor-acceptor pair spectra suggest the presence of deep acceptors, in addition to the two main shallower ones at about 0.23 eV. Similar spectra from Mg-doped GaN nanowires (NWs) grown by MOCVD are also demonstrated and briefly discussed.