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 spe ctrum, the enhancement of the yellow emission implies that most of the intr insic defects responsible for the yellow band exist mainly near the interfa ce between the buffer layer and the epilayer. We also found that the intens ity of the yellow luminescence decreases with increasing Si dopants, which is consistent with the fact that the microscopic origin of the yellow emiss ion can be attributed to gallium vacancies V-Ga. In additions, our investig ations reveal that the potential fluctuations, that give rise to the effect of band-gap narrowing and linewidth broadening, are mainly caused by rando mly distributed doping impurities instead of other defects. (C) 1999 Americ an Institute of Physics. [S0021-8979(99)09023-4].