Two dimensional materials such as graphene (Gr) and transition metal dichalcogenides (TMD) are promising building blocks for visible and near-infrared photodetection [1,2]. The integration of these 2d materials in vertical van der Waals heterostructures allows for original designs that rely on out-of plane photocarriers extraction. I will give an overview of the recent experimental works done on Gr/TMD/Gr photodetectors and discuss the photodetection schemes at stake for light excitation ranging from visible to near-infrared. For energies above the TMD bandgap, efficient absorption occurs in this semiconducting material while graphene sheets act as transparent electrodes that extract the photocarriers . For lower energies, light is only absorbed in graphene, where a hot electron distribution is created leading to photocurrent via thermionic emission at the Gr/TMD interface . Both mechanisms share an electrically tunable, ultrafast (few picoseconds timescale) and spatially scalable photoresponse that appears quite promising for future applications. Furthermore these studies on a prototype van der Waals heterostructure offer a unique understanding of the currently poorly known out-of-plane charge transport in homo- and hetero-layer stacks of 2d materials.
1. F. H. L. Koppens et al., Nature Nano 9, 10 (2014)
2. K. F. Mak et al., Nature Phot. 10, 216 (2016)
3. M. Massicotte et al., Nature Nano 11, 42–46 (2016).
4. M. Massicotte et al., Nature Comm 7, 12174 (2016)