Abstract
Charge transport in semi-insulating Pb2P2Se6 single crystals was investigated. The dark current was dominated by the ionization of deep-level defects within the gap of the material, with activation energies between 0.6 and 0.8 eV. A model for charge transport was developed where a continuum of these midgap defect levels determined the conductivity of Pb2P2Se6. Current-voltage characteristics in Pb2P2Se6 single crystals showed nonlinear behavior at high voltages. The nonlinear characteristics are attributed to competing Poole-Frenkel emission and phonon-assisted tunneling processes, such that at lower fields the former effect dominates, while at higher electric fields the latter mechanism emerges. Calculated tunneling times in the 250-500 fs range indicate that the deep traps promote weak electron-phonon coupling and that the tunneling involves deep defect levels. Transient multi-terahertz spectroscopy and temperature-dependent photoconductivity measurements reveal signatures of dispersive transport and low mobility on the order of 10 cm2/(V s), consistent with a disordered potential energy landscape in Pb2P2Se6. Photoresponse in these crystals is therefore limited by a distribution of trapping and recombination sites within the band gap.
Original language | English |
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Pages (from-to) | 1877-1887 |
Number of pages | 11 |
Journal | ACS Photonics |
Volume | 3 |
Issue number | 10 |
DOIs | |
Publication status | Published - Oct 19 2016 |
Keywords
- charge transport
- conductivity
- deep levels
- terahertz spectroscopy
- transient spectroscopy
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Biotechnology
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering