X-ray photoelectron diffraction on SiC and AlN epitaxial films: polytype structure and polarity

Angle-scanned X-ray photoelectron diffraction (XPD) is used to determine th e polytype and polarity of thin SiC and ALN films grown by molecular beam e pitaxy in {0001} orientation. For high-energy photoelectrons excited by Mg or Al K alpha radiation, the Si 2p and C Is diffraction patterns are differ ent for the polytypes (2H, 3C, 4H, 6H) and their polar faces. A medium-ener gy XPD pattern is sensitive to the atomic stacking of more than ten monolay ers and hardly affected by surface reconstruction or contamination. Thus, a clear fingerprint-like identification of the polytype and polarity is poss ible for a film thickness of only few nanometers. The diffraction patterns are well described by single-scattering cluster theory which allows the sim ulation of XPD patterns on any stacking sequences. (C) 2001 Elsevier Scienc e B.V. All rights reserved.