Abstract :
The adsorption of K on the n-GaAs(1 0 0) surface was investigated by X-ray photoelectron spectroscopy (XPS) and
synchrotron radiation photoemission spectroscopy (SR–PES). The Ga3d and As3d core level was measured for clean and K
adsorbed GaAs(1 0 0) surface. The adsorption of K induced chemical reaction between K and As, and the K–As reactant formed
when the K coverage u > 1 ML. The chemical reaction between K and Ga did not occur, but Ga atoms were exchanged by K
atoms. From the data of band bending, the Schottky barrier is 0.70 eV. The Fermi-level pinning was not caused by defect levels.
The probable reason is that the dangling bonds of surface Ga atoms were filled by the outer-shell electrons of K atoms, forming a
half-filled surface state. The Fermi-level pinning was caused by this half-filled surface state.
