GEOMETRY AND ELECTRONIC-STRUCTURE OF THE ARSENIC VACANCY ON GAAS(110)

Tunneling microscopy and spectroscopy, in conjunction with tight-bindi ng molecular dynamics, provide compelling evidence that the ''missing As'' defect on GaAs(110) is indeed an As vacancy. Neighboring Ga atoms relax upward by about 0.7 angstrom, but do not rebond. The defect is positively charged and most likely in a +2 state. Both the relaxation and the preponderance of As vacancies on p-GaAs are explained by the e nergetics of the defect levels. The essential features of the observat ions can be understood from qualitative arguments based on hybrid orbi tals.