Unoccupied surface states revealing the Si(111)3 3 -Al, -Ga, and -In adatom geometries

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- (T4) and the hollow- (H3) site adatom models. Good agreement between experiment and theory for the unoccupied surface-state band structures is found for the T4 model, which also has the lowest total energy. © 1987 The American Physical Society.