Effects of controlled surface states on the photoluminescence emission of GaN film

Hot phosphor acid (H3PO4) etching and/or SiOxNy surface passivation are used to change the surface states of high-resistance intrinsic GaN films. The films are investigated to reveal the influence of controlled surface states on photoluminescence (PL) emission. It is found that H3PO4 etching cannot improve the ultraviolet (UV) PL emission obviously, but the PL spectrum in the range of visible light is considerably enhanced. After passivation with SiOxNy film, the quantum efficiency of UV PL is increased by a factor of 12-13. Meanwhile, the visible PL is significantly enhanced. By analyzing the PL spectra of the etched and passivated samples obtained at room temperature and low temperatures, we discuss the role of surface states in PL emission in the range of UV, blue and yellow bands, and the related physical mechanisms.