PHOTOELECTRON SPECTROSCOPIC STUDY OF THE EFFECT OF Cs INTRALAYER ON THE BAND LINEUP OF Ge/InP(100) HETEROJUNCTION

The formation and band lineup of the Ge/InP(100) interface with or without alkali metal Cs intralayer (IL) are studied by means of X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). It is found that the Cs atoms do not react with or diffuse into the subatrate and the Ge overlayer. The thin Cs IL will induce an increase of the valence band offset (\DeltaE_v) for the Ge/InP(100) heterojunction. The changes of \DeltaE_v are proportional to the IL thickness and them saturate for IL thickness of about one half of a monolayer of Cs IL. Without the IL, \DeltaE_v of the Ge/InP(100) heterojunction is equal to 0.70eV, and \DeltaE_v with one half of monolayer IL is up to 0.90eV. These results show that the interface dipole plays a major role in the band lineup at the heterojunction interface.