Bandgap and optical absorption edge of GaAs{sub 1−x}Bi{sub x} alloys with 0 < x < 17.8%
- Department of Electrical and Computer Engineering, University of Victoria, Victoria, British Columbia V8W 2Y2 (Canada)
- Département de Physique, Université de Montréal, Montréal, Quebec H3C 3J7 (Canada)
- Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)
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.
- OSTI ID:
- 22402763
- Journal Information:
- Journal of Applied Physics, Vol. 116, Issue 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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