Photoemission from $p$-GaAs(001) with nonequilibrium cesium overlayer

The dependences of the photoemission current and effective electron affinity on the submonolayer cesium coverage at the adsorption of Cs on a GaAs(001) surface, as well as the kinetics of the photocurrent and affinity after the termination of Cs deposition, which is caused by the relaxation of the structure of a nonequilibrium adsorption layer, have been experimentally studied. The revealed features in the dependence of the photocurrent on the Cs coverage are attributed to a nonmonotonic behavior of the surface band bending in the Cs/GaAs(001) system. It has been established that a relaxation decrease in the photocurrent in the case of coverages smaller than half a monolayer is due to the relaxation of the band bending, whereas an increase in the photocurrent at larger coverages is caused by the relaxation of the electron affinity.