The relaxation of photodarkening (PD) brought about by above-bandgap and sub-bandgap excitations is studied in a wide temperature range in amorphous selenium (a-Se) films designed for avalanche photodetectors. The experimental results suggest that in contrast to sub-bandgap excitation, above-bandgap excitation does not cause the formation of self-trapped excitons, viz., photoinduced transformation of the a-Se ground state configuration into a metastable higher-energy configuration. For above-bandgap excitation only transient PD is observed, and its subsequent relaxation can be explained by thermalization and energy relaxation of uncorrelated carriers through the band-tails in order to restore the ground state configuration. In contrast, sub-bandgap excitation causes both transient and reversible PD, with the latter controlled by the formation of self-trapped excitons, whose relaxation requires overcoming an energy barrier of 0.78 ± 0.02 eV either by thermal activation (at elevated temperatures) or by configurational tunneling (for temperatures below room temperature).
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4 August 2014
Research Article|
August 08 2014
Comparative study of the photodarkening relaxation-kinetics in amorphous selenium for above-bandgap and sub-bandgap illumination
A. Mishchenko;
A. Mishchenko
a)
1Department of Physics,
Lakehead University
, 955 Oliver Road, Thunder Bay, Ontario P7B5E1, Canada
2
Thunder Bay Regional Research Institute
, 290 Munro Street, Thunder Bay, Ontario P7A7T1, Canada
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G. P. Lindberg;
G. P. Lindberg
3
SUNY at Buffalo, Department of Physics
, Buffalo, New York 14260-1500 USA
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B. A. Weinstein;
B. A. Weinstein
3
SUNY at Buffalo, Department of Physics
, Buffalo, New York 14260-1500 USA
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A. Reznik
A. Reznik
1Department of Physics,
Lakehead University
, 955 Oliver Road, Thunder Bay, Ontario P7B5E1, Canada
2
Thunder Bay Regional Research Institute
, 290 Munro Street, Thunder Bay, Ontario P7A7T1, Canada
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A. Mishchenko
1,2,a)
G. P. Lindberg
3
B. A. Weinstein
3
A. Reznik
1,2
1Department of Physics,
Lakehead University
, 955 Oliver Road, Thunder Bay, Ontario P7B5E1, Canada
2
Thunder Bay Regional Research Institute
, 290 Munro Street, Thunder Bay, Ontario P7A7T1, Canada
3
SUNY at Buffalo, Department of Physics
, Buffalo, New York 14260-1500 USA
a)
Electronic mail: [email protected]
Appl. Phys. Lett. 105, 051912 (2014)
Article history
Received:
June 26 2014
Accepted:
July 30 2014
Citation
A. Mishchenko, G. P. Lindberg, B. A. Weinstein, A. Reznik; Comparative study of the photodarkening relaxation-kinetics in amorphous selenium for above-bandgap and sub-bandgap illumination. Appl. Phys. Lett. 4 August 2014; 105 (5): 051912. https://doi.org/10.1063/1.4892836
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