Valence-band and surface electronic structure of CdTe

Angle-resolved uv photoelectron spectroscopy has been used to study the electronic structure of cleaved CdTe. Within a direct-transition model, valence-band states on the Γ–(K)–X line are probed in normal emission, yielding the energy of the critical points ${\Gamma }_7$ and ${\Gamma }_8$ and of the minimum of the spin-orbit-split second valence band. A relativistic augmented-plane-wave calculation including the effects of the Cd 4d states has been performed and is favorably compared with the experimental results. Through this comparison, the final-state bands are found to be well approximated with free-electron bands in the normal direction and in a 〈111〉 direction. Through extensive studies in off-normal emission at selected photon energies and under specific polarization geometries, two surface resonances located (in energy) close to, but below the valence-band edge and two surface states found in the open lens of the calculated projected valence-band structure, can be identified and mapped along the Γ¯–X¯’–M¯–X¯–Γ¯ boundary of the surface Brillouin zone (BZ). The resonance highest in energy is interpreted as due to the broken bond on the anion. Only weak emission from the surface resonances is observed in the first surface BZ. By comparing the experimental results with the calculation by Wang and Duke for ZnS(110), a description of the relaxation model for CdTe(110) is discussed.