AVS 51st International Symposium
    Semiconductors Wednesday Sessions
       Session SC-WeA

Paper SC-WeA4
Optical Properties of GaAs@sub 1-x@N@sub x@: A Tight Binding and Variable Angle Spectroscopic Ellipsometry Study

Wednesday, November 17, 2004, 3:00 pm, Room 304C

Session: Narrow Gap Semiconductors
Presenter: S. Turcotte, École Polytechnique de Montréal, Canada
Authors: S. Turcotte, École Polytechnique de Montréal, Canada
S. Larouche, École Polytechnique de Montréal, Canada
J.-N. Beaudry, École Polytechnique de Montréal, Canada
N. Shtinkov, École Polytechnique de Montréal, Canada
L. Martinu, École Polytechnique de Montréal, Canada
R.A. Masut, École Polytechnique de Montréal, Canada
R. Leonelli, Université de Montréal, Canada
P. Desjardins, École Polytechnique de Montréal, Canada
Correspondent: Click to Email
We have carried out a series of tight-binding (TB) calculations and variable-angle spectroscopic ellipsometry (VASE) measurements in order to investigate the excited states above the band gap of GaAs@sub 1-x@N@sub x@ layers on GaAs(001). The calculations are carried out using an empirical TB model in the sp@super 3@d@super 5@s*s@sub N@ parameterization, which provides a band-anticrossing description of the GaAs@sub 1-x@N@sub x@ band structure over the entire Brillouin zone for energies up to 5 eV above the valence band maximum. A series of fully-coherent GaAs@sub 1-x@N@sub x@ layers with x up to 0.012 were grown on GaAs(001) by organometallic vapor phase epitaxy using trimethylgallium, tertiarybutylarsine, and dimethylhydrazine precursors. The GaAsN dielectric function was reliably determined from 0.76 to 4.4 eV through point by point fitting of the experimental data with a model which also takes into account the GaAs substrate and the oxide overlayer. In addition to the band edge transition E@sub -@, the L point related optical transition E@sub 1@ and their split-off replica, we also observe, for the first time in room temperature VASE measurements, the E@sub +@ level signature which appears as a well defined critical point contribution to the dielectric function. The comparison between experimental data and TB calculations provides information on the specific contributions of the different Brillouin zone points to the GaAsN dispersion curves.