Sulfide passivation of III-V semiconductor surfaces: role of the sulfur ionic charge and of the reaction potential of the solution

A model is proposed for describing the effect of a solution on the electronic properties of sulfided surfaces of III-V semiconductors which treats the adsorption of sulfur in terms of a Lewis oxide-base interaction. According to this model, the density of states on a sulfided surface, which pin the Fermi level, decreases as the global hardness of the electron shell of the adsorbed sulfide ions is increased. The Thomas-Fermi-Dirac method is used to calculate the global hardness of sulfide ions with different charges as a function of the dielectric constant of the medium. It is shown that the hardness of a sulfur ion is greater when its charge is lower and the dielectric constant of the solvent is lower. (C) 1998 American Institute of Physics. [S1063-7842(98)02008 -X].