Comparative study of surface recombination in hexagonal GaN and ZnO surfaces.

Surface recombination in GaN and ZnO crystals was comparatively investigated using steady-state and time-resolved photoluminescence (PL) measurements. The measurements were performed for various surface orientations (+c, -c, and m-plane surfaces), and the measured PL intensity and lifetime showed distinct dependence on the surface orientation. The dependence clearly indicates that the surface recombination rate is modified by the effects of surface band bending. The results were also verified by numerical analysis using a rate equation model considering the diffusion of photoexcited carriers and their recombination processes on the surface and inside the crystal. [ABSTRACT FROM AUTHOR]