Surface structure and orbital symmetries of (110) surface states of GaAs

The orbital symmetries of (110) surface electronic states of GaAs for three different surface-relaxation models are analyzed using the tight-binding method. Although the atomic displacements involved in all three relaxations are basically very similar, they give rise to different orderings of some surface states when these states are characterized by their orbital symmetries. Angle-resolved photoemission measurements using polarized radiation therefore provide a useful tool for distinguishing between competing surface structures determined from low-energy electron-diffraction studies. A comparison of the recent, preliminary measurements by Williams and Lapeyre with our theoretical results shows that only the ’’bond-relaxation’’ model for the surface is in agreement with the experimental results. Local densities of surface states and the orbital symmetries of surface states are discussed.