Strong suppression of the yellow luminescence in C-doped GaN in air ambient

The authors observed a drastic reduction of the yellow luminescence (YL) intensity in carbon-doped semi-insulating GaN in air or oxygen ambient as compared to the intensity in vacuum. The YL intensity dropped about 300 times while the exciton emission remained almost unchanged. The authors assume that the donor-acceptor-pair transitions involving a gallium vacancy complex in a thin near-surface region cause the strong YL. Oxygen molecules or ions induce the surface states acting as a very efficient channel of nonradiative recombination. The results indicate that carbon may not be involved in the acceptor responsible for the YL band in GaN:C