IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Wednesday Sessions
       Session EL-WeA

Paper EL-WeA10
Initial Stages of Al@sub x@Se@sub y@ Heteroepitaxial Growth on Si(111)

Wednesday, October 31, 2001, 5:00 pm, Room 124

Session: Semiconductor Growth
Presenter: J.A. Adams, University of Washington
Authors: J.A. Adams, University of Washington
A.A. Bostwick, University of Washington
E. Rotenberg, Advanced Light Source, Berkeley
F.S. Ohuchi, University of Washington
M.A. Olmstead, University of Washington
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Aluminum selenide is a largely unstudied material with interesting possibilities as a wide band gap semiconductor. Bulk Al@sub 2@Se@sub 3@ has a 3.1 eV band gap, and its hexagonal lattice constant (defected wurtzite structure) is about 1.3% larger than Si(111). However, very little is known about the properties of Al@sub x@Se@sub y@ heteroepitaxial films. Unlike Ga@sub x@Se@sub y@, which is stable in both layered GaSe and defected zincblende Ga@sub 2@Se@sub 3@ structures, layered AlSe has not been reported in either bulk or thin film form. We have used an Al@sub 2@Se@sub 3@ evaporative source to deposit thin films of Al@sub x@Se@sub y@ on Si(111) by molecular beam epitaxy. We investigated their electronic and atomic structure using angle-resolved valence band and core-level spectroscopy and diffraction, and compare these results to our previous work on Ga@sub x@Se@sub y@/Si(111). The initial Al@sub x@Se@sub y@/Si interface appears to form a bilayer structure similar to GaSe-terminated Si, although the temperatures for bilayer formation and for Se-evaporation from the film are higher for AlSe than for GaSe. Surface states (resonances) are well within the bulk Si bands, at least 1.2 eV below the Fermi level at the zone center. Despite the initial lone-pair termination, subsequent growth leads to photoelectron diffraction forward-focussing peaks along directions expected for the covalently-bonded wurtzite structure and not for layered AlSe.