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

Abstract

It is demonstrated that the NEXAFS spectra are a "fingerprint" of the microstructure and the composition of the AlGaN and InGaN alloys. From the angular dependence of the NEXAFS spectra, the hexagonal symmetry of the compounds under study is deduced and the (px, py) or pz character of the final state is identified. The energy position of the absorption edge (Eabs) of the binary compounds depends on the cation atomic number. The Eabs of the AlGaN alloys takes values in between those corresponding to AlN and GaN, as was expected. Contrary to that, the absorption edge of In0.16Ga0.84N is red-shifted relative to that of GaN and InN, probably due to ordering and/or phase separation phenomena.