Two-dimensional electronic structure of the GaAs(110)-Bi system

The occupied electronic structure of the GaAs(110)-Bi(1×{}1) monolayer system has been studied using angle-resolved photoelectron spectroscopy with a synchrotron-radiation source. The overlayer system possesses at least three detectable surface states (S', S'' and S''') with two-dimensional character. Both the state with the lowest (S') and the state with the highest (S''') binding energy are clearly visible over a large portion of the (1×{}1) surface Brillouin zone. The intermediate state (S'') was observed along {Γ}{} X{} ' and also in the neighborhood of X{}. The intensity of all three states exhibits a predominantly pz-like dependence on the polarization of the synchrotron light. However, S''' possesses a greater component of pxy-like character than either S' or S''. At the zone center, S' is situated 0.5 eV above the valence-band maximum, and it disperses downwards by {}1.0 eV to X{}, and by {}0.8 eV to X{} '. At M{} it has its binding-energy maximum, 1.3 eV below the energetic position at {Γ}{}. The two-dimensional electronic structure of this system is compared with that of the closely related GaAs(110)-Sb(1×{}1) monolayer system and with the results of first-principles calculations.