Passivation of GaAs in alcohol solutions of ammonium sulfide

The chemical composition and position of the surface Fermi level in n- and p-type GaAs (100) under conditions of passivation in alcohol solutions of ammonium sulfide were studied by x-ray photoelectron and Raman spectroscopies. It is shown that sulfidizing GaAs decreases the amount of oxides on the surface, forms a sulfide coating on the surface, and decreases the surface barrier; in n-GaAs the surface Fermi level shifts in the direction of the conduction band and in p-GaAs it shifts in the direction of the valence band. It was established that as the permittivity of the sulfide solution decreases, the rate constant of the reaction, which leads to the formation of sulfides on the surface, and the magnitude of the shift of the surface Fermi level increase. The shift equals 0.53 eV in n-GaAs and 0.27 eV in p-GaAs in the case of passivation in a solution of ammonium sulfide in tret-butanol. A model explaining these experimental results on the basis of the reactivity of the sulfide ion in solution is proposed. (C) 1997 American Institute of Physics. [S1063-7826(97)01711-0].