Optical properties of Si-doped GaN films

Results of the front-side and back-side photoluminescence (PL) measurements in a set of Si-doped GaN epifilms are presented. From the back-side PL spectrum, the enhancement of the yellow emission implies that most of the intrinsic defects responsible for the yellow band exist mainly near the interface between the buffer layer and the epilayer. We also found that the intensity of the yellow luminescence decreases with increasing Si dopants, which is consistent with the fact that the microscopic origin of the yellow emission can be attributed to gallium vacancies V_Ga. In additions, our investigations reveal that the potential fluctuations, that give rise to the effect of band-gap narrowing and linewidth broadening, are mainly caused by randomly distributed doping impurities instead of other defects.