Evidence for a Type-II band alignment between cubic and hexagonal phases of GaN

The photoluminescence spectra of a series of thin, undoped, hexagonal GaN films containing cubic GaN inclusions grown by molecular-beam epitaxy on 6H-SiC have been studied as a function of temperature and excitation power. The dependence of the line shape and peak position of a peak at ∼3.17 eV on laser power suggests that it is associated with a spatially indirect Type-II transition between hexagonal and cubic GaN. The values of the band offsets extracted from our data are in good agreement with theoretical predictions.