Experimental determination of the valence-band structure of molecular-beam-epitaxy-grown CdTe(110).

Abstract

Angle-resolved synchroton-radiation photoemission spectroscopy was used to determine the electronic valence-band structure of CdTe(110) films grown by molecular-beam epitaxy. The high structural quality of the homoepitaxial films is represented in well-developed reflection high-energy electron diffraction patterns as well as in sharp and strong valence-band features. The experimental valence-band dispersion along the \ensuremath{\Gamma}KX direction was determined with use of a direct-transition model to free-electron-like final-state bands. The experimental band structure agrees well with pseudopotential calculations if the final-state band is lowered by a muffin-tin potential of ${E}_{0}$=5.7 eV. A photoemission structure \ensuremath{\sim}1 eV below the Fermi level is related to the emission from the top of the ${\ensuremath{\Gamma}}_{8}$ valence band. The intensity of that transition correlates strongly with the crystalline quality of the CdTe(110) surfaces. No evidence was found for surface-state emission at normal as well as off-normal emission at high-symmetry points of the surface Brillouin zone. A small but noticeable dispersion of the Cd 4d levels indicates a slight bonding character of these core states in CdTe.