A method was demonstrated for the determination of the charge state of As vacancies, on the (110) surfaces of p-type material, by using scanning tunnelling microscopy. The method was based upon a balance between hole depletion at isolated As vacancies and hole accumulation at ionized dopant atoms whose charge states were known. Detailed analysis revealed a one-to-one balance between charged vacancies and ionized dopants; thus indicating an isolated As vacancy charge of +1. It was suggested that this method could be extended so as to determine the quantitative charge states of other (positive or negative) point defects.

K.J.Chao, A.R.Smith, C.K.Shih: Journal of Vacuum Science and Technology B, 1996, 14[2], 948-52. See also: K.J.Chao, A.R.Smith, C.K.Shih: Physical Review B, 1996, 53[11], 6935-8