Ferroelectric localized field enhanced nanowire photodetectors

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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.

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.

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.

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").

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.

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.

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.

Additionally, the device also shows the advantages of fast-response, stability at room temperature, low power consumption and so on.

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.