SULFIDE PASSIVATION OF ILL-V SEMICONDUCTORS - THE STARTING ELECTRONIC-STRUCTURE OF A SEMICONDUCTOR AS A FACTOR IN THE INTERACTION BETWEEN ITS VALENCE-ELECTRONS AND THE SULFUR ION

In the experiments on GaAs, InP, and GaP treated in aqueous solutions of Na2S:9H2O, it has been shown that in the process of sulfide passivation of III-V semiconductors a significant role is played by both the starting electronic structure of the semiconductor surface (prior to sulfidizing) and the energy state of the sulfur ion in solution. A model of the interaction of the sulfur ion in a solution with the valence electrons of a III-V semiconductor in the course of the sulfidizing process has been suggested and verified. During the interaction process, a change takes place in the electrochemical potential (Fermi level) of the semiconductor, which affects the electron work function at the surface. Between various semiconductors the amount of this change in the work-function value varies in proportion to the negative of the starting electron work-function value in the untreated semiconductor and depends on the treatment temperature. In a semiconductor such that its starting work-function value is equal to the effective electronegativity of the sulfur ion in solution, the work function will not be changed by sulfidization. The effective electronegativity of the sulfur ion in solution depends on the ionicity of the chemical bonds of the semiconductor being treated.