Comparison of Cs adsorption on GaAs (1 0 0), Ga0.5Al0.5As (0 0 1) and GaN (0 0 0 1) surfaces

Through the calculation based on the first principle density functional theory, differences between Cs adsorption on GaAs (1 0 0), Ga0.5Al0.5As (0 0 1) and GaN (0 0 0 1) surfaces are investigated. Calculation results show Cs coverage has certain effects on the atomic structure, adsorption energy, surface work function, dipole moment and total density of states. As Cs coverage increases, the work function lowers first and then increases, and GaN (0 0 0 1) surface gets the minimum work function at the soonest, Ga0.5Al0.5As (0 0 1) is the last to get the minimum value. The dipole moments of three surfaces at different Cs coverages are compared in detail, the comparison show the change trends are well consistent. The similarities and differences of total density of states of the surfaces are investigated and compared. In addition, to verify the calculation results, the Cs-only activation experiment is also performed, the photocurrent curves got during the activation process confirm the correctness of the calculation result.