Evidence of compensating centers as origin of yellow luminescence in GaN

The dependence of the near-band edge and the yellow luminescence in n-type GaN grown by organometallic vapor-phase epitaxy is investigated as a function of doping concentration. The band edge and yellow luminescence intensity increase as the doping concentration is increased. However, the band-edge-to-yellow luminescence ratio does not change significantly as the doping concentration is increased by two orders of magnitude. A theoretical model based on rate equations is developed for the band-edge-to-yellow intensity ratio. Analysis of the experimental data in terms of the model reveals that the concentration of the level causing the yellow luminescence increases linearly with doping concentration. This dependence shows that the yellow luminescence is due to a compensating center.