A. Kozikov: Interlayer exciton optoelectronics in van der Waals heterostructures

ABSTRACT:The field of novel two-dimensional (2D) materials has grown enormously for the last several years. The technology to build van der Waals heterostructures out of them enables development of new devices combining unique properties of individual 2D crystals. It has allowed producing vertical tunnelling transistors, nanometre-thick light emitting diodes, high quality field-effect transistors and others. A lot of exotic physical phenomena have been observed in these heterostructures, such as, for example, the Hofstadter butterfly effect, viscous electron backflow, unconventional superconductivity.

In this talk, I will focus on optoelectronic properties of 2D materials, semiconducting transition metal dichalcogenides (TMDCs) in particular. I will present experimental results of the electrical control of excitons in heterostructures based on WSe2 and MoS2, which is done using vertical light-emitting diodes. Because of the type-II band alignment of MoS2/WSe2 heterostructures, spatially indirect excitons (IEs) form, in which electrons and holes reside in different materials. I will discuss the electrically induced emission of the IEs and their behaviour as a function of the bias voltage and separation between MoS2and WSe2. The physical mechanism of charge carrier injection into these materials differs depending on experimental conditions, which leads to unexpected effects in luminescence spectra.