ANISOTROPY OF THE NITROGEN CONDUCTION STATES IN THE GROUP-III NITRIDES STUDIED BY POLARIZED X-RAY-ABSORPTION

The energy distribution of the nitrogen antibonding electron states in the hexagonal epitaxial layers of AlN, GaN, and InN and cubic epitaxi al layers of GaN and InN along p(xy) plane and p(z) direction is repor ted. The study was performed by the polarized x-ray absorption at the K edge of N. A strong polarization dependence of the absorption spectr a indicating the significant anisotropy of the conduction band was fou nd in the case of hexagonal samples. Very weak polarization dependenci es observed in cubic samples correspond well with the defect distribut ion anisotropy. Qualitatively different and cation dependent antibondi ng states distribution point out the role played by a contribution of hybridized cation-nitrogen electronic states to the individual conduct ion bandstructures of AlN, GaN, and InN. (C) 1997 American Institute o f Physics.