Optical properties of graphene/GaN hybrid structures

Abstract

We studied the optical properties of GaN epilayers covered by one-atom-thick graphene layer which was prepared by chemical vapor deposition. The free-exciton A (FXA) emission peak in the photoluminescence (PL) spectra of GaN was found to split into two peaks with a large overlapping at medium temperature range (40K150K). We also measured time-resolved photoluminescence, power-dependent photoluminescence and reflectance spectra, implying that the origin of the split peak was more related to the FXA emission in GaN. Besides, the controversial peak at 3.484 eV (for 1.5K) below the donor-bound exciton emission peak in PL spectra exhibited strong dependence on temperature. The carrier lifetime of this abnormal line in the hybrid structure was much shorter than as-grown GaN layer which possibly accounted for the enhancement of the relative PL intensity. Considering the intensive research on the electrical properties of graphene-semiconductor interfaces recently, our results are meaningful for the applications of optoelectronic devices. Such applications are promising because of the great mechanical and thermal stabilities of graphene.