Luminescence measurements in aqueous solutions were performed upon n-GaN layers grown on sapphire substrates and on Si substrates. Photoluminescence measurements at n-GaN/sapphire and n-GaN/Si electrodes showed an identical emission band centered at 2.20eV (the well-known yellow luminescence band), showing that the same deep acceptor level was present in both materials. Additional reddish luminescence was observed when the holes were injected from the solution [electroluminescence (EL)], which may be ascribed to the occurrence of radiative (near) surface recombination. From an analysis of the potential dependence of both the photoluminescence and EL intensity of the 2.20eV band, it may be concluded that this band possessed a significant contribution from the (near) surface.

Defect Luminescence at n-GaN Electrodes - a Comparative Study Between n-GaN Grown on Sapphire Substrates and on Si Substrates. I.M.Huygens, W.P.Gomes, K.Strubbe: Journal of the Electrochemical Society, 2006, 153[1], G72-7