- Turkish Journal of Physics
- Vol: 44 Issue: 4
- Investigating above-bandgap and below-bandgap optical transition in GaBiAs epilayers by photoreflect...
Investigating above-bandgap and below-bandgap optical transition in GaBiAs epilayers by photoreflectance spectroscopy
Authors : Ömer Dönmez, Ayşe Erol
Pages : 384-393
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Publication Date : 9999-12-31
Article Type : Makaleler
Abstract :We present optical identification of deep level defects in as-grown and annealed GaBixAs1−x(x=0, 0.013 and 0.015) alloys grown at different temperatures (220 °C and 320 °C) by using photo-modulated reflectance (PR) spectroscopy and photoluminescence (PL). The PR measurements are employed at above- and below-bandgap excitations, and the PR line-shape is analyzed by the third derivative functional form (TDFF). The PR at below-bandgap excitation reveals transitions at 0.757 ±0.001 eV and 0.710 ±0.002 eV at 30K and 300K, respectively. Franz-Keldysh oscillations are observed in all samples under above-bandgap excitation at PR measurements, and the built-in electric field, which may originate from the charged As-antisite defects is calculated from local extrema points in the PR spectra. The decrease in the built-in electric field after thermal annealing is explained with decreased point defect density.Keywords : Dilute bismide alloys, GaBiAs, deep level defect, antisite defect, photoreflectance