Observation of highly dispersive surface states on GaN(0001)1x1

The electronic structure of n-type, Si-doped, wurtzite GaN(0001)1X1 surface s has been studied using synchrotron radiation excited angle-resolved photo emission. The GaN thin films were grown by metal-organic chemical-vapor dep osition on SiC. Two previously unobserved surface bands were measured and f ully characterized. One of the states is highly nonlocalized, dispersing th roughout much of the valence band along the <(Gamma)over bar>-(K) over bar- (M) over bar and <(Gamma)over bar>-(M) over bar directions of the 1X1 surfa ce Brillouin zone. The identification of these states as surface bands was confirmed both by their lack of dispersion perpendicular to the surface, an d by the sensitivity of the states to hydrogen adsorption. The symmetry pro perties of the states were determined using the linear polarization of the incident synchrotron radiation. These states are quite distant from the loc alized nondispersive surface state previously observed on GaN. [S0163-1829( 99)50824-2].