N- and Ga-K-edge XAFS study of the effect of annealing on In implanted GaN



GaN implanted with In, with fluencies (Φ) in the range of 1×1014 to 1×1016cm-2, is studied by means of X-ray absorption fine structure spectroscopy (XAFS). The heavily implanted samples, which are either highly defective or amorphous, are also studied after annealing at temperatures up to 1000 °C. The extended XAFS (EXAFS) spectra recorded at the Ga-K-edge reveal that the coordination numbers decrease with Φ while the Debye-Waller factors increase accordingly. Annealing at 1000 °C of the sample implanted with Φ = 1×1015cm-2recovers the coordination numbers and Debye-Waller factors to the values of the as-grown sample. Contrary to that, annealing even at 1000 °C does not induce recovery of the local coordination of Ga in the amorphized layers, although significant improvement in the EXAFS parameters is observed. In this case the detected undercoordination of Ga reveals loss of nitrogen after implantation and/or annealing. Annealing also improves the N-K-edge near edge (NEXAFS) spectra of the heavily implanted samples. More specifically, the NEXAFS peaks become sharper and the resonance lines that have been attributed to N-split-interstitials and N2 disappear even at low annealing temperatures. However, the absence of angular dependence of the NEXAFS spectra of the annealed layers, that became amorphous after the implantation, reveals the formation of randomly oriented microcrystallites. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)