Nonequilibrium Carrier Dynamics in Transition Metal Dichalcogenide Semiconductors

TL;DR

This paper investigates the ultrafast carrier relaxation processes in transition metal dichalcogenide semiconductors, revealing that strong Coulomb interactions lead to rapid carrier scattering, impacting optoelectronic device performance.

Contribution

It combines ab-initio band-structure calculations with many-body theory to predict carrier relaxation times in TMD semiconductors, providing insights into their ultrafast dynamics.

Findings

Carrier relaxation occurs on a 50-fs timescale.

Coulomb scattering is significantly faster than in quantum wells.

Rapid scattering challenges population inversion for lasing.

Abstract

When exploring new materials for their potential in (opto)electronic device applications, it is important to understand the role of various carrier interaction and scattering processes. Research on transition metal dichalcogenide (TMD) semiconductors has recently progressed towards the realisation of working devices, which involve light-emitting diodes, nanocavity lasers, and single-photon emitters. In these two-dimensional atomically thin semiconductors, the Coulomb interaction is known to be much stronger than in quantum wells of conventional semiconductors like GaAs, as witnessed by the 50 times larger exciton binding energy. The question arises, whether this directly translates into equivalently faster carrier-carrier Coulomb scattering of excited carriers. Here we show that a combination of ab-initio band-structure and many-body theory predicts carrier relaxation on a 50-fs time scale, which is less than an order of magnitude faster than in quantum wells. These scattering times compete with the recently reported sub-ps exciton recombination times, thus making it harder to achieve population inversion and lasing.