Adsorption of Cs on GaAs-based (001) surfaces: electronic structure of activation layer

Polar semiconductor surfaces with planes parallel to the surface similar to GaAs (001) surface which is formed by either Ga or As atomic layers, are technologically important. This type of surface can be prepared by molecular beam epitaxy (MBE). Among different orientations the (001) surface is the one that is used widely in optoelectronic devices. Despite of intensive investigation of GaAs (001) surface its structural and electronic properties are under debate up to now. A number of the first principle total energy investigations of GaAs (001) surface have been reported. However, the theoretical studies of the polar semiconductor surface encounter many difficulties. For the surface simulation a slab model is usually used. In this case several problems emerged and the first one is a charge transfer between two surfaces of the slab. Relative position and dispersion of the surface state bands can be changed by the effect of electrostatic potential due to charge transfer. Another problem is the interaction of two surface states with each other through the slab. In order to exclude the manifestations of its interaction, the usage of a thick slab is necessary. Different models were developed for calculations of GaAs (001) surface. The main goal of the present report is to provide the mechanism of Cs and Sb adsorption on the GaAs (100) surface and the electron structure (ES) of the activation layer during the oxygen coadsorption. The influence of the substrate composition on the work function is also investigated.