Evolution of electron states at doped semiconductor surfaces in a depletion-layer formation process

Abstract

Adsorption on a doped semiconductor surface often gives rise to gradual formation of a carrier-depletion layer at the surface. By calculating the carrier density distribution and the effective one-electron potential at each stage with the local-density-functional formalism, we investigate the evolution of electron states at doped semiconductor surfaces through the whole formation process of a carrier-depletion layer. At an early stage of this formation process, the carrier density rises quickly from zero and forms a prominent peak near the surface as a function of distance from the surface. At a late stage, the carrier density rises slowly and monotonically up to its bulk value in its profile curve, and its rising rate significantly depends upon temperature, namely the degree of degeneracy of carriers. After reaching the final stage, the profile curve of the carrier density makes a rigid shift into the inside with its form unchanged with further increase in thickness of the depletion layer.