New insight in the metal-semiconductor interface formation: Generation and removal of donor-like surface states on Cs/p-GaAs(001)
Photoreflectance spectroscopy is applied for detailed measurements of the evolution of surface band bending φ s under cesium adsorption and desorption on the As-rich and Ga-rich p-GaAs(001) surfaces. Two new observations are reported. Firstly, under Cs adsorption on the Ga-rich p-GaAs(100) surface with the (4×2)/c(8×2) reconstruction, the dependence of φ s on the Cs coverage 9 contains several maxima and minima, which were not observed earlier for adsorbate-semiconductor interfaces. Secondly, the dependence φ(θ) has a shape of a reproducible hysteresis loop under the adsorption of cesium and its subsequent thermodesorption. The results are discussed in connection with the experimental data on the atomic structure of the Cs/GaAs(001) interface and possible mechanisms of generation and removal of Cs-induced donor-like surface states. © 2007 American Institute of Physics.