Optical constants and critical-point parameters of GaAs1-xSbxalloy films grown on GaAs

✍ Scribed by Ben Sedrine, N. ;Gharbi, T. ;Harmand, J. C. ;Chtourou, R.

• Book ID: 105364756
• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 417 KB
• Volume: 205
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200777746

✦ Synopsis

Abstract

Spectroscopic Ellipsometry (SE) is used in this work to investigate the optical properties of the GaAs~1–x~ Sb__~x~__ alloys. The present study is based on a set of GaAs~1–x~ Sb__~x~__ 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 GaAs~1–x~ Sb__~x~__ alloys were extracted using the Newton–Raphson method based on the four‐phase model (ambient – GaAs native oxide overlayer – GaAs~1–x~ Sb__~x~__ film – GaAs substrate). Analytic line shapes fitted to numerically calculated second derivatives of the dielectric functions determined the critical‐points parameters above the GaAs~1–x~ Sb__~x~__ bandgap E~0~. The best fit parameters and the experimental extracted data show in particular a red‐shift and a broadening increase of E~1~, E~1~ + Δ~1~, E ′~0~ and E~2~ transitions by increasing Sb content. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)