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Title: Bandgap and optical absorption edge of GaAs{sub 1−x}Bi{sub x} alloys with 0 < x < 17.8%

The compositional dependence of the fundamental bandgap of pseudomorphic GaAs{sub 1−x}Bi{sub x} layers on GaAs substrates is studied at room temperature by optical transmission and photoluminescence spectroscopies. All GaAs{sub 1−x}Bi{sub x} films (0 ≤ x ≤ 17.8%) show direct optical bandgaps, which decrease with increasing Bi content, closely following density functional theory predictions. The smallest measured bandgap is 0.52 eV (∼2.4 μm) at 17.8% Bi. Extrapolating a fit to the data, the GaAs{sub 1−x}Bi{sub x} bandgap is predicted to reach 0 eV at 35% Bi. Below the GaAs{sub 1−x}Bi{sub x} bandgap, exponential absorption band tails are observed with Urbach energies 3–6 times larger than that of bulk GaAs. The Urbach parameter increases with Bi content up to 5.5% Bi, and remains constant at higher concentrations. The lattice constant and Bi content of GaAs{sub 1−x}Bi{sub x} layers (0 < x ≤ 19.4%) are studied using high resolution x-ray diffraction and Rutherford backscattering spectroscopy. The relaxed lattice constant of hypothetical zincblende GaBi is estimated to be 6.33 ± 0.05 Å, from extrapolation of the Rutherford backscattering spectrometry and x-ray diffraction data.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ; ;  [3] ;  [4] ;  [1]
  1. Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)
  2. (Canada)
  3. Department of Electrical and Computer Engineering, University of Victoria, Victoria, British Columbia V8W 2Y2 (Canada)
  4. Département de Physique, Université de Montréal, Montréal, Quebec H3C 3J7 (Canada)
Publication Date:
OSTI Identifier:
22402763
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ALLOYS; DENSITY FUNCTIONAL METHOD; FILMS; GALLIUM ARSENIDES; LATTICE PARAMETERS; LAYERS; PHOTOLUMINESCENCE; RUTHERFORD BACKSCATTERING SPECTROSCOPY; SUBSTRATES; TEMPERATURE RANGE 0273-0400 K; X-RAY DIFFRACTION; ZINC SULFIDES