Defect Luminescence at n-GaN Electrodes: A Comparative Study Between n-GaN Grown on Sapphire Substrates and on Si Substrates

Abstract

Luminescence measurements in aqueous solutions were performed upon n-GaN layers grown on sapphire substrates and on Si substrates. Photoluminescence (PL) measurements at n- and n- 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.