Abstract
We present a self-powered, high-performance graphene-enhanced ultraviolet silicon Schottky photodetector. Different from traditional transparent electrodes, such as indium tin oxides or ultra-thin metals, the unique ultraviolet absorption property of graphene leads to long carrier life time of hot electrons that can contribute to the photocurrent or potential carrier-multiplication. Our proposed structure boosts the internal quantum efficiency over 100%, approaching the upper-limit of silicon-based ultraviolet photodetector. In the near-ultraviolet and mid-ultraviolet spectral region, the proposed ultraviolet photodetector exhibits high performance at zero-biasing (self-powered) mode, including high photo-responsivity (0.2 A W−1), fast time response (5 ns), high specific detectivity (1.6 × 1013 Jones), and internal quantum efficiency greater than 100%. Further, the photo-responsivity is larger than 0.14 A W−1 in wavelength range from 200 to 400 nm, comparable to that of state-of-the-art Si, GaN, SiC Schottky photodetectors. The photodetectors exhibit stable operations in the ambient condition even 2 years after fabrication, showing great potential in practical applications, such as wearable devices, communication, and “dissipation-less” remote sensor networks.
Highlights
Ultraviolet (UV) photodetectors could find a wide range of applications,[1,2,3,4,5,6,7,8] such as environmental monitoring,[3] biological and chemical analysis,[4] flame detection,[5] astronomical studies,[8] internet-of-things sensors,[9] and missile detection.[10]
Silicon is a widely-used semiconductor material for UV detectors owing to its suitable bandgap, low-density surface states, high reliability, matured manufacturing, and high-speed detection.[17,18,19,20,21]
Our proposed structure boosts the internal quantum efficiency over 100%, approaching the upper-limit of silicon-based ultraviolet photodetector
Summary
Ultraviolet (UV) photodetectors could find a wide range of applications,[1,2,3,4,5,6,7,8] such as environmental monitoring,[3] biological and chemical analysis,[4] flame detection,[5] astronomical studies,[8] internet-of-things sensors,[9] and missile detection.[10]. A typical silicon PN junction depth (XJ) is larger than 200 nm.[22] As the penetration depth of UV light in Si is less than 20 nm for λ < 370 nm,[23] the photo-generated carriers are primarily near the Si surface and need to diffuse (~100 nm scale) into the junction region, resulting in significant carrier recombination and limiting the performance. We did not use the effective Richardson constant to describe the Gr/Si long lifetime of photo-induced hot carriers especially in the UV wavelength range These hot carriers contribute to photocurrent in graphene and result in higher internal quantum efficiency (IQE), Schottky junction, because the traditional Richardson constant A* overestimates the thermionic dark current of graphene/silicon Schottky junction without considering the finite density of states which facilitates to break through the upper-limit of traditional of graphene, which should be better accounted by using the silicon UV photodetector.
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