Observation of highly dispersive surface states on GaN(0001)1×1

The electronic structure of n-type, Si-doped, wurtzite GaN(0001)1×1 surfaces has been studied using synchrotron radiation excited angle-resolved photoemission. The GaN thin films were grown by metal-organic chemical-vapor deposition on SiC. Two previously unobserved surface bands were measured and fully characterized. One of the states is highly nonlocalized, dispersing throughout much of the valence band along the $\overline{\Gamma }-\overline{K}-\overline{M}$and $\overline{\Gamma }-\overline{M}$ directions of the 1×1 surface Brillouin zone. The identification of these states as surface bands was confirmed both by their lack of dispersion perpendicular to the surface, and by the sensitivity of the states to hydrogen adsorption. The symmetry properties of the states were determined using the linear polarization of the incident synchrotron radiation. These states are quite distant from the localized nondispersive surface state previously observed on GaN.