The band structure of InN has been investigated by comparing the calculated valence-band density of states with x-ray photoemission spectroscopy (XPS) of the valence-bands. The band structure of InN has previously been calculated using density functional theory (DFT) within the local density approximation (LDA) [1]. Such calculations result in an overlap of the conduction and valence bands around the Γ-point, giving rise to negative band gaps. The overlap is due to the overestimation of the pd-repulsion within the DFT-LDA [2]. Pseudo-potentials accounting for the self-interaction corrections of the In4d electrons were used to revise the amount of pd-repulsion, avoiding the overestimation [1]. The percentage contribution of the pd-repulsion was determined by comparing the experimental and theoretical positioning of the In4d valence-levels with respect to the valence band maximum (VBM). Here, the true experimental In4d - VBM separation is reported as 16.0 ± 0.2 eV, in contrast to a previous value of 14.9 eV [3]. The valence-band density of states was calculated using DFT-LDA, with the revised pd-repulsion for the self-interaction corrections included. Good agreement between the experimental and theoretical valence-band density of states was obtained. Previous such studies of InN were hampered by the difficulty in preparing InN free surfaces. Conventional methods of surface preparation are severely limited for InN. Here atomic hydrogen cleaning (AHC) cycles were used, which have been shown to successfully prepare clean, electronic-damage free InN surfaces [4]. A combination of core-level XPS, scanning electron microscopy and atomic force microscopy confirmed that AHC produced clean, flat, featureless surfaces.

[1] F. Bechstedt, J. Furthmüller, J. Cryst. Growth 246, 315 (2002)

[2] I. Mahboob et al., Phys. Rev. B 69, 201307(R) (2004)

[3] Q. X. Guo et al., Phys. Rev. B 58, 15304 (1998)

[4] L. F. J. Piper et al., J. Vac. Sci. Technol.A, in press (2005)