SURFACE-BARRIER AND POLARIZATION EFFECTS IN THE PHOTOEMISSION FROM GAAS(110)

We have developed a theory of photoemission from III-V compound semiconductors within the one-step model and discuss the effect of transition-matrix elements, final states, and the surface barrier on the energy distribution of photoelectrons. As a prototype the (110) surface of GaAs is studied, and theoretical spectra are compared with experiment in normal as well as in non-normal emission. The specific position of the interface vacuum crystal, appearing in the calculation of the transition-matrix elements, influences the shape of the spectra considerably. The energy-distribution curves strongly depend on the escape angles of the photoelectrons as well as the incidence angles of the radiation leading to significant intensity variations especially of the dangling-bond surface state. Band-mapping methods prove to be misleading, in the worst cases by an error of about 100 meV in the estimation of the valence-band energies. The corrugated surface barrier is also investigated; our analysis favors a smooth saturated image potential barrier.