EFFECT OF SURFACE-LAYER ON OPTICAL-PROPERTIES OF GAN AND INXGA1-XN UPON THERMAL ANNEALING

We investigated the effect of rapid thermal annealing (RTA) on the opt ical properties of GaN and InxGa1-xN. It was found that some of the ch anges in the photoluminescence spectra of GaN upon annealing were asso ciated with the properties of the surface layer. For example, a new lo w-temperature photoluminescence line associated with donor-acceptor pa ir (DAP) recombination appeared at around 3.40 eV upon annealing, but disappeared after etching off the surface layer. This indicates that t he acceptors responsible for the DAP emission were created only near t he surface. After the RTA process, the near-band-edge emission was blu eshifted, and the relative intensity of yellow luminescence with respe ct to the near-band-edge emission was increased, which were also attri buted to the influence of the surface layer. The thermal annealing eff ect of an InxGa1-xN multiple quantum well structure is also discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)05139-0].