AVS 49th International Symposium
    Electronic Materials and Devices Wednesday Sessions
       Session EL+SS+SC-WeA

Paper EL+SS+SC-WeA1
Scanning Tunneling Microscopy and Spectroscopy of Gallium Oxide and Indium Oxide Deposition on GaAs(001)-(2x4)

Wednesday, November 6, 2002, 2:00 pm, Room C-107

Session: Semiconductor Film Growth and Oxidation
Presenter: M.J. Hale, University of California, San Diego
Authors: M.J. Hale, University of California, San Diego
J.Z. Sexton, University of California, San Diego
S.I. Yi, Applied Materials
D.L. Winn, University of California, San Diego
A.C. Kummel, University of California, San Diego
Correspondent: Click to Email
The surface structures formed upon deposition of Ga@sub 2@O and In@sub 2@O onto the technologically important As-rich GaAs(001)-(2x4) surface have been studied using scanning tunneling microscopy (STM) and spectroscopy (STS), low energy electron diffraction (LEED), and density functional theory (DFT) calculations. At submonolayer coverage, the initial bonding sites are different for Ga@sub 2@O and In@sub 2@O adsorptions due to the different activation barriers for the two oxides to chemisorb at various sites onto the surface. In@sub 2@O initially bonds in the trough between the arsenic dimer rows, whereas Ga@sub 2@O first inserts into the top layer arsenic dimer rows. Conversely, at elevated surface temperatures, both Ga@sub 2@O and In@sub 2@O form a crystalline monolayer. Both oxides form crystalline (2x1) surface reconstructions that are electronically unpinned: there are no states within the band gap. Although both oxides form a (2x1) surface reconstruction, the surface structures differ. At monolayer coverage the Ga@sub 2@O/GaAs surface has a much larger step density while the In@sub 2@O/GaAs surface shows a broad distribution of row oxide spacing. The DFT calculations confirm the observed surface structures and show that both oxides form unpinned surfaces because the bonding to these oxides restore the charge on the first and second layer As and Ga atoms to near bulk values.