Luminescence measurements in aqueous solutions were performed upon n-GaN layers grown on sapphire substrates and on Si substrates. Photoluminescence (PL) measurements at n-GaN/ sapphire and n-GaN/ Si electrodes show an identical emission band centered at 2.20 eV (the well- known yellow luminescence band), showing that the same deep acceptor level is present in both materials. Additional reddish luminescence is observed when the holes are 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 PL and EL intensity of the 2.20-eV band, it may be concluded that this band possesses a significant contribution from the (near) surface. (c) 2005 The Electrochemical Society. [DOI: 10.1149/ 1.2135218] All rights reserved.