SULFIDATION MECHANISM OF PRE-CLEANED GAAS SURFACE USING (NH4)(2)S-X SOLUTION

Wet cleaning and successive sulfidation of GaAs with (NH4)(2)S-x solut ion were carried out in air or in an atmosphere controlled glove box w ith nitrogen, respectively. The wet cleaned GaAs was revealed to conta in oxide and/or elemental forms of As and/or Ga. Successive sulfidatio n with (NH4)(2)S-x brought about a large decrease of surface oxides an d elemental forms, and the occurrence of As-S and/or Ga-S bonds. The f ormation of passivation layer with sulfur was shown to be mainly depen dent on the surface state of wet cleaned GaAs before the sulfidation, and especially on the presence of elemental As and Ga. The amount of s ulfur bonds with As and Ga was determined by the quantity of elemental form of As and Ga generated during the surface preparation for the su lfidation. X-ray photoelectron spectroscopy was employed to investigat e a chemical bonding state of wet etched and sulfidation treated GaAs surface. (C) 1997 Elsevier Science S.A.