Transition metal dichalcogenides (TMDs) exhibit optoelectronic properties that vary strongly with sample thickness. By using them in Van der Waals heterostructures, we can custom-build novel devices perfectly tailored to the study of interlayer electron-hole pair (exciton) generation. Efficient generation of interlayer excitons could be used to make novel photodetectors, electroluminescent emitters, or excitonic integrated circuits. In this work, we observed efficient multiplication of interlayer excitons by hot electron relaxation across the interface of a Van der Waals heterostructure. Electronic transport measurements showed large negative differential conductance, source-drain and gate voltage dependent interlayer current, and strong temperature dependence, all of which support hot electron relaxation as the interlayer exciton generation mechanism.

Atomically thin semiconductors such as few-layered molybdenum ditelluride (MoTe₂) inspire new fields of research in condensed matter physics as well as materials science. Both fields share common interest in procuring atomically thin semiconductors with a tunable, finite band gap. Single layer MoTe₂ exhibits a band gap in the near infrared range, allowing for further research into electron-hole pairs in a 2D setting. Like other transition metal dichalcogenides (TMD), MoTe₂ exhibits a transition from an indirect band gap to a direct band gap as the material reaches the monolayer limit. In this work, we have successfully manufactured two and three layered MoTe₂ heterostructures by micro-mechanical exfoliation and semi-dry contact alignment transfer. With selected flakes, semi-dry transfer contact is done by the stacking of selected flake specimens using a custom transfer microscope to create heterojunctions. Hexagonal boron nitride is used in heterostructure synthesis to serve as a tunneling promoter to graphene. After heterostructure assembly, resultant structures are analyzed by measuring optical and optoelectronic response.