Donor-acceptor pair emission enhancement in mass-transport-grown GaN

A dominating donor-acceptor pair (DAP) emission at about 3.27 eV is observed in the photoluminescence and cathodoluminescence spectra of intentionally undoped mass-transport (MT)-grown GaN, while only a weak presence of the DAP emission is recorded in the as-grown hydride vapor phase epitaxial GaN. A comparative study of impurity and native defect incorporation in the as-grown and MT GaN was performed, showing a significant increase of oxygen and empty clusters involving Ga vacancy and oxygen in the MT GaN. Based on the observed results as well as on doping analysis of the structure and kinetic analysis of the emission intensities, we propose an acceptorlike complex, creating a state as a semiclassical potential well near the valence-band top due to the local tensile strain caused by the empty clusters to be responsible for the dominating behavior of the DAP emission