Abstract
There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared. Thermal photodetectors, such as bolometers, have emerged as the technology of choice, because they do not need cooling. The performance of a bolometer is linked to its temperature coefficient of resistance (TCR, ∼2–4% K−1 for state-of-the-art materials). Graphene is ideally suited for optoelectronic applications, with a variety of reported photodetectors ranging from visible to THz frequencies. For the mid-infrared, graphene-based detectors with TCRs ∼4–11% K−1 have been demonstrated. Here we present an uncooled, mid-infrared photodetector, where the pyroelectric response of a LiNbO3 crystal is transduced with high gain (up to 200) into resistivity modulation for graphene. This is achieved by fabricating a floating metallic structure that concentrates the pyroelectric charge on the top-gate capacitor of the graphene channel, leading to TCRs up to 900% K−1, and the ability to resolve temperature variations down to 15 μK.
Highlights
There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared
A single-layer graphene (SLG) channel with source and drain contacts is fabricated on the pyroelectric substrate (500 mm-thick z-cut lithium niobate (LN)) as described in Methods
A 10 nm-thick Al2O3 dielectric layer isolates the SLG from an H-shaped floating Au structure designed to overlap the oxide-coated SLG in the centre, whereas lateral pads are placed in direct contact with the substrate
Summary
There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared. We present an uncooled, mid-infrared photodetector, where the pyroelectric response of a LiNbO3 crystal is transduced with high gain (up to 200) into resistivity modulation for graphene. This is achieved by fabricating a floating metallic structure that concentrates the pyroelectric charge on the top-gate capacitor of the graphene channel, leading to TCRs up to 900% K À 1, and the ability to resolve temperature variations down to 15 mK. Pyroelectric detectors are low-cost, uncooled thermal PDs for the mid-infrared (MIR)[1,2,12] They are capacitor-like structures where a pyroelectric crystal is sandwiched between two metal electrodes[2].
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