Photodetectors based on two-dimensional (2D) layered materials have been widely studied since the discovery of graphene due to their atomic layer thicknesses, strong light-matter interactions and layer-dependent electronic and optical properties\[1,2\]. A variety of high performance photodetectors with ultrahigh responsivity or gain, ultrahigh detectivity have been reported based on transition metal dichalcogenides (TMDs), III–VI group layered semiconductors, black phosphorus and so on, from visible to mid-infrared wavelength range\[3,4\]. Thus far, these 2D photodetectors with high responsivity are operated in photoconductive mode with high gain (including photogating mode), which suffer from either a large dark current or a slow response speed. Further, a bias is required for the device operation resulting in a static power dissipation, unsuitable for self-powered or portable battery-powered devices. A good photodetector should currently possess a high responsivity, a short response time, a high signal-to-noise ratio and low or no power consumption for practical applications. Photodiode detectors are the ideal choice for satisfying the above requirements. 2D materials based van der Waals heterostructures (vdWHs) offer an innovative avenue for this photodetection via the photovoltaic effect. However, the EQE (or power conversion efficiency) of those 2D heterodiodes is still low, most below 55% (5%) due to the severe tunneling-assisted interface recombination of the photogenerated electron-hole pairs in such thin bilateral depletion regions as well as the inefficient carrier selective contacts because of the Schottky barrier at the semiconductor-metal interface. In addition, in these heterodiodes with bilateral depletion regions, both the photogenerated electrons and holes need to cross the heterointerface where they are easily trapped, leading to a slow response speed. To resolve these problems, in this work we propose and design a heterodiode with a unilateral depletion region. The proposed heterodiode is made of a narrow bandgap highly-doped 2D semiconductor (BP) and a p-type MoS~2~, where the BP is served as an effective carrier selective contact without any heterointerface barrier for photogenerated electrons and MoS~2~ is for light absorption. In this case, only electrons generated in the MoS~2~ cross the heterointerface and collected by the BP via the rapid recombination with the holes in the accumulation region. Thus, the interface recombination of the photogenerated electron-hole pairs could be significantly suppressed and the response speed could be greatly promoted. When upon 520 nm laser illumination, the heterodiode exhibits a pronounced photovoltaic effect with a short-circuit current as high as 1.3 μA and a large open-circuit voltage of 0.61 V, enabling an ultrahigh photocurrent to dark current ratio over 1×10^6^. Specifically, a high responsivity of 0.3 A W^-1^ and a high external quantum efficiency of 71% are obtained under zero bias. Remarkably, a high power conversion efficiency of 9% and a fast response time of 9 μs are achieved, which, to the best of our knowledge, are the highest values ever reported for photovoltaic detectors based on 2D vdWHs.

 

References

\[1\]Koppens, F. H. L. *et al.* Photodetectors based on graphene, other two-dimensional materials and hybrid systems. *Nature Nanotechnology* 9, 780 (2014).

\[2\]Huo, N. & Konstantatos, G. Recent Progress and Future Prospects of 2D-Based Photodetectors. *Advanced Materials* 30, 1801164 (2018).

\[3\]Long, M., Wang, P., Fang, H. & Hu, W. Progress, Challenges, and Opportunities for 2D Material Based Photodetectors. *Advanced Functional Materials* 0, 1803807 (2018).

\[4\]Wu, F. *et al.* AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity. *Advanced Functional Materials* 29, 1900314 (2019).


High Performance Photovoltaic Detectors Based on Van Der Waals Heterojunctions

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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