Two-Dimensional Material Photodetectors: High Responsivities and Short Response Times of Graphene/Multilayer MoS₂ Heterostructures

High Resolution Image Download MS PowerPoint Slide Wafer-scale and 1-, 3-, and 6-layer MoS 2 films are prepared through the sulfurization of amorphous MoS 2 on sapphire substrates. After transferring a 1-layer of graphene to the MoS 2 films, photodetectors with MoS 2 light absorption and graphene carrier transport layers are fabricated. Compared with the low responsivity values of the standalone MoS 2 device, a 10 6 responsivity enhancement is observed for the devices with MoS 2 absorption and one-layer graphene carrier transport layers. The phenomenon is attributed to the ultrashort transit time of carriers in the graphene layer and the relatively long carrier lifetime in the MoS 2 layer, which will result in a large photoconductive gain for the graphene/MoS 2 photodetector. Through repeating 3-layer MoS 2 transferring, a device with a 6-layer MoS 2 absorption layer and a 1-layer graphene carrier transport layer can be fabricated. The excess electron storage in the multilayer MoS 2 will help to achieve the charge neutrality in the light absorption layer, and, therefore, the response times of the device would reduce from >50 ms (1-layer MoS 2 ) to below 10 ms (6-layer MoS 2 ). The high detectivity of up to 2 × 10 10 Jones of the device has demonstrated the potential of such 2D material heterostructures for photodetector applications at room temperature with high photoconductive gain compatible with avalanche photodetectors.