Surface band bending at nominally undoped and Mg-doped InN by Auger electron spectroscopy

Non intentionally doped and Mg-doped InN layers were analyzed by sputter depth profiling in an Auger electron spectroscopy (AES) equipment and by Ultra-violet photoelectron spectroscopy (UPS). On the surface of both types of layers a high concentration of oxygen and a strong accumulation of electrons was observed, however, in contrast to the undoped layers the conductivity profile of Mg doped InN shows a strong discontinuity close to the surface. The depth of this discontinuity strongly depends on the oxygen concentration. The energy shift of the In. peak was estimated during the depth profiling in order to obtain information about the position of the Fermi level. In the bulk of the Mg-doped InN the In-MNN peak shift of about 0.15 eV demonstrates the influence of the Mg on the Fermi level, while the surface is clearly n-type. A strong shift of the Fermi level close to the surface was observed, which might be attributed to the formation of In2O3. By the combination of AES and UPS a model for the band bending is proposed, which demonstrates that Mg doping indeed can compensate the n-type conductivity in the bulk and is therefore a prospective candidate to achieve p-type doping in InN. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.