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Photoconductive laser spectroscopy as a method to enhance defect spectral signatures in amorphous oxide semiconductor thin- film transistors

Dhara, Soumen, Niang, Kham M., Flewitt, Andrew J., Nathan, Arokia and Lynch, Stephen A. 2019. Photoconductive laser spectroscopy as a method to enhance defect spectral signatures in amorphous oxide semiconductor thin- film transistors. Applied Physics Letters 114 (1) , 011907. 10.1063/1.5070141

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Abstract

Defects in semiconductor thin-films often leave optical spectral signatures that can be used for their identification. In this letter, we report on spectrally resolved photoconductivity measurements of amorphous oxide semiconductor thin-film transistors. In contrast to previously reported photoconductive spectroscopy measurements recorded using spectrally filtered broadband light sources, we used a wavelength tunable picosecond laser to illuminate the thin-film. We extracted the absorption coefficient as a function of wavelength from the photocurrent measurement and showed that it followed the typical characteristic behaviour previously reported for amorphous oxide semiconductor thin-films. However, in addition, we observed several sharp spectral peaks in the photoconductivity spectrum which can be associated with sub-bandgap defects. These enhanced peaks are not normally visible in previously reported photoconductivity spectra. Furthermore, we show that we can control the sensitivity of our measurement by changing the applied gate bias voltage when the thin-films were fabricated into transistors. The enhancement achieved by using the wavelength tunable laser makes this a particularly sensitive characterisation tool and can additionally be used to discriminate between defects which have been incorporated after device fabrication.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: AIP Publishing
ISSN: 0003-6951
Date of First Compliant Deposit: 18 December 2018
Date of Acceptance: 18 December 2018
Last Modified: 30 Sep 2022 14:10
URI: https://orca.cardiff.ac.uk/id/eprint/117765

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