Selective excitation of the yellow luminescence of GaN

The yellow luminescence of n-type GaN has been studied with selective excitation using a combination of Ar`-ion and dye lasers. Narrower structures whose peak energies follow the excitation photon energy over the width of the yellow luminescence have been observed. Unlike the yellow luminescence excited by the above band gap excitations, these "ne structures exhibit thermal activated quenching behavior. We propose that these "ne structures are due to emission occurring at complexes of shallow donors and deep acceptors which can be resonantly excited by photons with energies below the band gap. The activation energy deduced from their intensity is that for delocalization of electrons out of the complexes. Our results therefore suggest that there is more than one recombination channel (usually assumed to be due to distant donor}acceptor pairs) to the yellow luminescence in GaN. ( 1999 Elsevier Science B.V. All rights reserved.