THE ELECTRONIC-STRUCTURE OF THE INP(110) SURFACE STUDIED BY SCANNING TUNNELING MICROSCOPY AND SPECTROSCOPY

The electronic structure of the InP(110) surface was investigated by scanning tunneling microscopy (STM) and spectroscopy (STS). Atomic resolution images were simultaneously obtained for the occupied A5 and the empty C3 surface states localized at the P and the In atoms, respectively, to determine their relative positions within the unit cell. The In surface state C3 was shifted by approximately 0.21 nm in the [001] direction, while in the [110BAR] direction the positions are unchanged as compared to a bulk plane. Neither the A5 nor the C3 states are localized in the band gap. An analysis of the inverse decay length as a function of the sample voltage revealed that the A5 state is a resonance at the GAMMA-BAR point of the surface Brillouin zone. In the [110BAR] direction it was spatially delocalized and resembled a Bloch state. The C3 state is localized at the edge of the surface Brillouin zone and resembled a Mott state. The existence of an indirect surface-band gap is supported by these measurements. The influence of the predominant orbital quantum number on the corrugation height was analyzed. The observed corrugation can be explained if it is assumed that the A5 state is a p-type state and the C3 state is characterized by a more s-type state. This allows us to explain the lower resolution of the In sublattice as compared to the P sublattice observed in scanning tunneling microscopy measurements.