Photoluminescence of Nanoporous GaN Films Prepared by Electrochemical Etching

Nanoporous (NP) GaN is prepared by electrochemical etching on a GaN epilayer grown on a sapphire substrate by metal-organic chemical vapor deposition. Scanning electron microscopy reveals that the average pore diameter and inter-pore spacing are approximately 25 and 45 nm, respectively. The photoluminescence (PL) spectra show that in contrast to the initial as-grown GaN epilayer, the NP GaN exhibits a high near-band-edge UV intensity, significant relaxation of compressive strain, and a lower yellow luminescence intensity. Both the line shape and line width of the PL spectra are almost the same for these two samples. The high quality of the NP GaN can be explained by the enhancement of the PL extraction efficiency and the decrease of impurity and defect density after etching.