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Open AccessArticle

A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices

Department of Chemistry and Physics, Coastal Carolina University, Conway, SC 29528, USA
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Author to whom correspondence should be addressed.
Sensors 2013, 13(8), 9921-9940; https://doi.org/10.3390/s130809921
Received: 31 May 2013 / Revised: 26 July 2013 / Accepted: 29 July 2013 / Published: 5 August 2013
(This article belongs to the Special Issue Photodetectors)
We present a phenomenological model for the photocurrent transient relaxation observed in ZnO-based metal-semiconductor-metal (MSM) planar photodetector devices based on time-resolved surface band bending. Surface band bending decreases during illumination, due to migration of photogenerated holes to the surface. Immediately after turning off illumination, conduction-band electrons must overcome a relatively low energy barrier to recombine with photogenerated holes at the surface; however, with increasing time, the adsorption of oxygen at the surface or electron trapping in the depletion region increases band bending, resulting in an increased bulk/surface energy barrier that slows the transport of photogenerated electrons. We present a complex rate equation based on thermionic transition of charge carriers to and from the surface and numerically fit this model to transient photocurrent measurements of several MSM planar ZnO photodetectors at variable temperature. Fitting parameters are found to be consistent with measured values in the literature. An understanding of the mechanism for persistent photoconductivity could lead to mitigation in future device applications. View Full-Text
Keywords: zinc oxide; ZnO; ultraviolet; photodetector; persistent photoconductivity; photoresponse zinc oxide; ZnO; ultraviolet; photodetector; persistent photoconductivity; photoresponse
MDPI and ACS Style

Moore, J.C.; Thompson, C.V. A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices. Sensors 2013, 13, 9921-9940.

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