Abstract
Graphene/silicon Schottky junctions have been proven efficient for photodetection, but the existing high dark current seriously restricts applications such as weak signal detection. In this paper, a thin layer of gadolinium iron garnet (Gd3Fe5O12, GdIG) film is introduced to engineer the interface of a graphene/silicon Schottky photodetector. The novel structure shows a significant decrease in dark current by 54 times at a −2 V bias. It also exhibits high performance in a self-powered mode in terms of an Ilight/Idark ratio up to 8.2 × 106 and a specific detectivity of 1.35 × 1013 Jones at 633 nm, showing appealing potential for weak-light detection. Practical suitability characterizations reveal a broadband absorption covering ultraviolet to near-infrared light and a large linear response with a wide range of light intensities. The device holds an operation speed of 0.15 ms, a stable response for 500 continuous working cycles, and long-term environmental stability after several months. Theoretical analysis shows that the interlayer increases the barrier height and passivates the contact surface so that the dark current is suppressed. This work demonstrates the good capacity of GdIG thin films as interlayer materials and provides a new solution for high-performance photodetectors.
Highlights
Photodetectors with high detectivity and large on-off ratios have urgent market demand in the field of weaksignal detection, remote sensing, and optical communications1–3
Benefiting from its natural planar membrane-like structure, low-cost Schottky junctions are conveniently constructed when transferring graphene onto n-type silicon, which generates photocarriers based on the photovoltaic effect6,7
Previous studies have found that graphene/silicon (Gr/Si) Schottky photodetectors usually have difficulty providing both high responsivity and detectivity since the detectivity is mainly limited by the dark current, which closely depends on the contact interface and the Schottky barrier height8
Summary
Photodetectors with high detectivity and large on-off ratios have urgent market demand in the field of weaksignal detection, remote sensing, and optical communications. Benefiting from its natural planar membrane-like structure, low-cost Schottky junctions are conveniently constructed when transferring graphene onto n-type silicon, which generates photocarriers based on the photovoltaic effect. Previous studies have found that graphene/silicon (Gr/Si) Schottky photodetectors usually have difficulty providing both high responsivity and detectivity since the detectivity is mainly limited by the dark current, which closely depends on the contact interface and the Schottky barrier height. The insertion of a thin insulating oxide layer at the interface has been demonstrated to be effective in engineering the Schottky junction and suppressing dark current. Li et al first utilized a natural oxide layer (SiO2) as an interlayer, which reduced the dark current from 9.35 nA to 0.1 nA, but the inevitable ever-growing thickness would block the tunneling of photogenerated carriers soon afterward. Graphene oxide flakes were inserted into the Gr/Si Schottky photodetector, which lowered the
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