Graphene/HgTe Quantum-Dot Photodetectors with Gate-Tunable Infrared Response

Graphene-based vertical heterostructures are of great interest as emerging electronic and optoelectronic devices. Here, we report the study of photovoltaic response from graphene/HgTe quantum-dot junction. The graphene/HgTe quantum-dot junction combines the high carrier mobility of graphene and tunable infrared optical absorption of HgTe colloidal quantum dots, which offers promising route for the next-generation infrared optoelectronics. We demonstrate that both the sign and magnitude of the short-circuit photocurrents and open-circuit voltages can be controlled by the applied gate voltage, which tunes the Fermi level and the interfacial built-in potential across the junction. The interfacial energy band diagram is deduced to provide the fundamental understanding of the essential physics behind the graphene/quantum-dot film junction.