Combining high responsivity and low power consumption in graphene-based photodetectors

Researchers from AMO GmbH, ICFO- Institut de Ciencies Fotoniques, RWTH Aachen University, and Bergishe Universität Wuppertal have developed a novel approach for graphene-based photodetectors that allows combining high responsivity and low power consumption, thus circumventing one of the major limitations of state-of-the-art photodetectors based on graphene – namely the high power-consumption caused by their large dark currents.

Sktech of the novel graphene-based photodetector with high responsivity and low power consumption.
Side-view sketch of the novel graphene-based photodetector, indicating the geometry of the single-layer graphene (SLG), of the metal electrodes, and of the layer of colloidal quantum dots (CQDs).

The strategy is to use an absorption layer formed by colloidal quantum dots (CQD) to photosensitize metal-insulator-graphene (MIG) diode. When light hits the MIG/QD device, a fraction of light gets absorbed and generates electron-hole pairs in the CQD layer. A fraction of these photo-generated carriers is then transferred to the underlying graphene layer and cause a shift of the chemical potential of the graphene. Thanks to the low density of states of graphene near the neutrality point, this shift can be relatively large and cause a dramatic change in the amount of current flowing across the diode, as this depends exponentially on the height of the diode barrier.

This new photodetection scheme permits dark currents of hundreds of nA up to few μA – orders of magnitude lower than other graphene-based photodetectors – while keeping responsivities almost two orders of magnitude higher compared to germanium on silicon and indium gallium arsenide infrared photodetectors (around 70A/W in the infrared). This combination of properties makes the approach very appealing for applications where high responsivity and low power consumption are required.

The work has been published on ACS Nano

Bibliographic Information:

Graphene–Quantum Dot Hybrid Photodetectors with Low Dark-Current Readout
D. De Fazio, B. Uzlu, I. Torre, C. Monasterio, S. Gupta, T. Khodkov, Y. Bi, Z. Wang, M. Otto, M. C. Lemme, S. Goossens, D. Neumaier, and F. H. L. Koppens
ACS Nano 2020