k-resolved inverse-photoemission spectroscopy has been used to determine the empty surface-state band structures of Si(111)√3 × √3 -Al, -Ga, and -In surfaces. The results are compared with first-principles pseudopotential total-energy and electronic-structure calculations for energy-minimized geometries of the filled- ($T_4$) and the hollow- ($H_3$) site adatom models. Good agreement between experiment and theory for the unoccupied surface-state band structures is found for the $T_4$ model, which also has the lowest total energy.

• Received 30 September 1986

DOI:https://doi.org/10.1103/PhysRevB.35.4137