AVS 49th International Symposium
    Surface Science Thursday Sessions
       Session SS+EL-ThM

Paper SS+EL-ThM5
Electronic and Structural Properties of Aluminum Selenide Ultrathin Film on Si(111)

Thursday, November 7, 2002, 9:40 am, Room C-110

Session: Structure of Semiconductor Surfaces & Interfaces
Presenter: J.A. Adams, University of Washington
Authors: J.A. Adams, University of Washington
A.A. Bostwick, University of Washington
T. Ohta, University of Washington
A. Klust, University of Washington
E. Rotenberg, Advanced Light Source
F.S. Ohuchi, University of Washington
M.A. Olmstead, University of Washington
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The wide band gaps of aluminum selenide and gallium selenide make them appealing candidates for blue-green opto-electronics, and they are closely lattice matched to silicon making them compatible in silicon-based structures and devices. However, very little is known about the properties of aluminum selenide heteroepitaxial films. Bulk aluminum selenide, a defected wurtzite structure, has a 3.1 eV band gap, and its hexagonal lattice constant is about 1.3% larger than Si(111). Unlike gallium selenide, 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 investigated varying thicknesses of ultrathin films of aluminum selenide grown epitaxially on Si(111) including sub-monolayer growth, a single bilayer, and the subsequent initial stages of growth on the bilayer. The AlSe/Si interface forms 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. The reactivity of the AlSe terminated Si(111) surface with both residual gases and for subsequent film growth is much higher than that of GaSe. Further deposition of aluminum selenide produces films that resemble the bulk stochiometry Al@sub 2@Se@sub 3@. Electronic band-structure for AlSe/Si was investigated using angle resolved photoelectron spectroscopy (ARPES). Unlike GaSe/Si, the AlSe bilayer appears to have a true surface state. Si-Al bond lengths and Al-Se bond lengths were measured by energy dependent photoelectron diffraction (EDPD). Initial results indicate that the Al-Si bond is 8% larger that in Al/Si(111)-(@sr@3x@sr@3). Heterostructures of AlSe/GaSe on Si(111) will also be discussed. Funded by NSF Grant DMR-0102427.