| Posted: Mar 31, 2016 |
Ferroelectric localized field enhanced nanowire photodetectors
(Nanowerk News) In recent years, one-dimensional semiconductor nanowires have been widely applied in photodetectors due to their excellent optoelectronic characteristics such as tunable light absorption, fast-response, and efficient light-to-current conversion. However, defect-induced intrinsic carriers and surface trapped charges at certain level result in appreciable dark currents, thus lowering the ratio of light to dark current (Ilight/Idark), limiting the detection performance of the photodetectors.
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Therefore, it is an urgent need to develop a unique device structure that can deplete the concentration of those defect/trap induced carriers, and thus increase signal-to-noise ratio and detectivity of nanowire based photodetectors.
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Now, a research team based at the Shanghai Institute of Technical Physics (SITP), has designed a high-performance nanowire photodetector with side-gated structure by combining ferroelectric materials and nanowires, and the as-fabricated device can be employed to reduce the dark current and increase the sensitivity of the photodetectors.
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The results have been published in the March 17, 2016 online edition of Nano Letters ("When Nanowires Meet Ultrahigh Ferroelectric Field–High-Performance Full-Depleted Nanowire Photodetectors").
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The researchers designed and fabricated a novel type of ferroelectric-enhanced side-gated single nanowire photodetectors for the first time. The intrinsic carriers in the nanowire channel can be fully depleted by the ultra-high electrostatic field from polarization of P(VDF-TrFE) ferroelectric polymer. In this scenario, the dark current is significantly reduced and thus the sensitivity of the photodetector is increased even when the gate voltage is removed.
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Utilizing this device structure, a typical single InP nanowire photodetector exhibits high photoconductive gain of 4.2 × 105, responsivity of 2.8 × 105 A W-1 and specific detectivity (D*) of 9.1 × 1015 Jones at λ = 830 nm.
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To further demonstrate the universality of the configuration, ferroelectric polymer side-gated single CdS nanowire photodetectors have been fabricated and demonstrated with ultra-high photoconductive gain of 1.2 × 107, responsivity of 5.2 × 106 A W-1 and D* up to 1.7 × 1018 Jones at λ = 520 nm.
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Additionally, the device also shows the advantages of fast-response, stability at room temperature, low power consumption and so on.
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These results demonstrate a new generic device structure design that can lead to controllable, full-depleted, high-performance and low power consumption nanowire photodetectors for a broad application.
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