Nitrogen K-edge NEXAFS measurements on group-III binary and ternary nitrides

It is demonstrated that the NEXAFS spectra are a "fingerprint" of the microstructure and the composition of the ternary alloys In0.16Ga0.84N and AlyGa1-yN (y=0.25, 0.5) and the parent binary compounds GaN, AlN and InN. From the angular dependence of the N K-edge NEXAFS spectra, the hexagonal symmetry of the under study compounds is deduced and the (p(x), p(y)) or p(z) character of the final state is identified. The energy position of the absorption edge (E-abs) of the binary compounds GaN, AlN and InN is found to red-shift linearly with the atomic number of the cation. The E-abs of the AlyGa1-yN alloys takes values in between those corresponding to the parent compounds AW and GaN. Contrary to that, the E-abs of In0.16Ga0.84N is red-shifted relative to that of GaN and InN, probably due to ordering and/or phase separation phenomena. (C) 1999 Elsevier Science B.V. All rights reserved.