SURFACE-STATE BAND-GAP OF INP(110) BY POLARIZED SURFACE DIFFERENTIAL REFLECTIVITY

We present surface-differential-reflectivity results on the polarization dependence of optical transitions on InP(110) surfaces in the energy range between 2.0 and 4.0 eV. The surface dielectric function has been computed for light electric-field vectors along the [110BAR] and [001] directions. The data show two anisotropic peaks at 2.6 eV (excited with the light electric-field vector along the [110BAR] direction) and 3.5 eV (excited with the light electric-field vector along the [001] direction), and an almost isotropic behavior for the peak at 3.1 eV and the shoulder at 2.9 eV. From a comparison with photoemission data and calculated surface-state wave functions, an optical surface-state band gap of 2.6 eV can be assigned to the X point in the surface Brillouin zone.