Valence band photoemission, band bending, and ionization energy of GaAs(100) treated in alcoholic sulfide solution

Abstract

Valence band and Fermi level position on a p-GaAs(100) surface treated in the solution of ammonium sulfide in isopropanol have been studied by ultraviolet photoemission spectroscopy. Sulfur treatment and subsequent annealing affect features of 0.8 and 3.7 eV binding energy in normal emission valence band spectrum of a bare semiconductor and the effect is related to the variation of surface chemical bonds. It has been found that after sulfur treatment surface band bending and ionization energy increase by 0.4 and 0.3 eV, respectively. Annealing at 310 °C or higher results in the decrease of the ionization energy with the temperature. The position of the surface Fermi level sharply changes from 1.5–1.20 to 0.85 eV above the valence band maximum when the surface is annealed at 360 °C.