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 ${\mathit{p}}_{\mathit{z}}$-like dependence on the polarization of the synchrotron light. However, S’ ’ ’ possesses a greater component of ${\mathit{p}}_{\mathit{x}\mathit{y}}$-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.