Ultra-thin van der Waals crystals as semiconductor quantum wells

TL;DR

This paper demonstrates the use of ultra-thin van der Waals crystals as quantum wells, enabling precise control of electronic subbands and high-quality transport, paving the way for atomically thin IR and THz light sources.

Contribution

It introduces the concept of quantum wells in 2D van der Waals heterostructures with InSe layers, revealing their subband structure through novel tunnelling and optical devices.

Findings

Revealed full subbands structure via resonance features

Achieved high-quality electronic transport in 2D quantum wells

Enabled potential development of atomically thin IR and THz light sources

Abstract

Control over the electronic spectrum at low energy is at the heart of the functioning of modern advanced electronics: high electron mobility transistors, semiconductor and Capasso terahertz lasers, and many others. Most of those devices rely on the meticulous engineering of the size quantization of electrons in quantum wells. This avenue, however, hasn't been explored in the case of 2D materials. Here we transfer this concept onto the van der Waals heterostructures which utilize few-layers films of InSe as quantum wells. The precise control over the energy of the subbands and their uniformity guarantees extremely high quality of the electronic transport in such systems. Using novel tunnelling and light emitting devices, for the first time we reveal the full subbands structure by studying resonance features in the tunnelling current, photoabsorption and light emission. In the future, these systems will allow development of elementary blocks for atomically thin infrared and THz light sources based on intersubband optical transitions in few-layer films of van der Waals materials.