AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA9
Competition Between Passivating and Etching in Halogen Reactions with III-V Semiconductor Surfaces

Tuesday, November 3, 1998, 4:40 pm, Room 308

Session: Semiconductor Surface Chemistry
Presenter: W.K. Wang, University of California, Riverside
Authors: W.K. Wang, University of California, Riverside
W.C. Simpson, Pacific Northwest National Laboratory
J.A. Yarmoff, University of California, Riverside
Correspondent: Click to Email
Halogen adsorption on III-V semiconductor surfaces with certain reconstructions leads to the formation of an ordered overlayer, while other III-V surfaces become disordered and etch. It has been suggested that the initial atomic structure and stoichiometry play important roles in determining whether a surface passivates or etches. A single crystal face of a given III-V material can have many surface reconstructions, each of which has a slightly different stoichiometry in the outermost few atomic layers. In this study, a direct comparison is made of the adsorption of halogens on different reconstructions of the same material. From the results, the microscopic mechanism underlying the predilection for ordering or disordering can be ascertained. Synchrotron-based soft x-ray photoelectron spectroscopy and low energy electron diffraction were employed to investigate surfaces following reaction. These techniques provide information about the chemical bonding and ordering on the surface. For example, for I@sub 2@ reaction with the In-terminated InAs(100)-c(8x2) surface, a well-ordered (1x1) structure forms and all of the iodine attaches to In. The As-terminated InAs(100)-c(2x8) surface, on the other hand, becomes disordered and iodine attaches to both In and As atoms. This can be explained by a preference for iodine to initially bond with the electron-deficient group III In atoms. In contrast, I@sub 2@ reaction produces ordered structures on both the Ga-terminated and As-terminated GaAs(100) surfaces. Cl@sub 2@ reactions almost always lead to etching after sufficient exposures, no matter what the initial surface structure, although following small exposures some ordered structures may form. In this presentation, the microscopic mechanisms underlying this behavior will be discussed.