Visible-to-near-infrared photodetector based on graphene-MoTe₂-graphene heterostructure

Graphene and transition metal dichalcogenides (TMDs), two-dimensional materials, have been investigated wildely in recent years. As a member of the TMD family, MoTe₂ possesses a suitable bandgap of~1.0 eV for near infrared (NIR) photodetection. Here we stack the MoTe₂ flake with two graphene flakes of high carrier mobility to form a graphene-MoTe₂-graphene heterostructure. It exhibits high photo-response to a broad spectrum range from 500 nm to 1300 nm. The photoresponsivity is calculated to be 1.6 A/W for the 750-nm light under 2 V/0 V drain-source/gate bias, and 154 mA/W for the 1100-nm light under 0.5 V/60 V drain-source/gate bias. Besides, the polarity of the photocurrent under zero V_ds can be efficiently tuned by the back gate voltage to satisfy different applications. Finally, we fabricate a vertical graphene-MoTe₂-graphene heterostructure which shows improved photoresponsivity of 3.3 A/W to visible light.