Surface and bulk electronic structure of thin-film wurtzite GaN

The bulk and surface valence-band electronic structure of thin-wurtzite GaN has been studied using angle-resolved photoemission spectroscopy. The bulk band dispersion along the Gamma Delta A, Gamma Sigma M, and Gamma TK directions of the bulk Brillouin zone was measured. Our results indicate the local-density approximation band-structure calculations using partial-core corrections for the Ga 3d states predict the relative dispersion of many of the observed bands with a high degree of accuracy. Furthermore, a nondispersive feature was identified near the valence-band maximum in a region of k space devoid of bulk states. This feature is identified as emission from a surface state on GaN(0001)-(1x1). The symmetry of this surface state is even with respect to the mirror planes of the surface and polarization measurements indicate that it is of sp(z) character, consistent with a dangling-bond state. [S0163-1829(97)03640-0].