Optical constants and critical-point parameters of GaAs1–xSbx alloy films grown on GaAs

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Abstract

Spectroscopic Ellipsometry (SE) is used in this work to investigate the optical properties of the GaAs1–xSbx alloys. The present study is based on a set of GaAs1–xSbx layers (x = 0.0%, 6.7% and 10.8%) grown on GaAs substrate by molecular beam epitaxy (MBE). The SE measurements were carried out in the energy range of 1.4 – 5.5 eV at room temperature for 70° and 75° incident angles, before and after chemical etching. The optical constants of GaAs1–xSbx alloys were extracted using the Newton–Raphson method based on the four-phase model (ambient – GaAs native oxide overlayer – GaAs1–xSbx film – GaAs substrate). Analytic line shapes fitted to numerically calculated second derivatives of the dielectric functions determined the critical-points parameters above the GaAs1–xSbx bandgap E0. The best fit parameters and the experimental extracted data show in particular a red-shift and a broadening increase of E1, E1 + Δ1, E0 and E2 transitions by increasing Sb content. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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