Tail state mediated conduction in zinc tin oxide thinfilm phototransistors under below bandgap optical excitation
Niang, Kham M.
Flewitt, Andrew J.
Lynch, Stephen A.
Nature Publishing Group UK
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Dhara, S., Niang, K. M., Flewitt, A. J., Nathan, A., & Lynch, S. A. (2021). Tail state mediated conduction in zinc tin oxide thinfilm phototransistors under below bandgap optical excitation. Scientific Reports, 11 (1)https://doi.org/10.1038/s41598-021-98339-4
Abstract: We report on the appearance of a strong persistent photoconductivity (PPC) and conductor-like behaviour in zinc tin oxide (ZTO) thinfilm phototransistors. The active ZTO channel layer was prepared by remote plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~ 10−4 A (a photo-to-dark current ratio of ~ 107) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor-like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~ 10−7 to 0.92/Ω/cm. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep states and tail states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-bandgap tail states of the ZTO in the strong PPC, while deep states contribute to mild PPC.
Article, /639/301/1005, /639/301/1005/1007, /639/624/399, article
Engineering and Physical Sciences Research Council (EP/M013006/1)
External DOI: https://doi.org/10.1038/s41598-021-98339-4
This record's URL: https://www.repository.cam.ac.uk/handle/1810/328489