Tuning of impurity-bound interlayer complexes in a van der Waals heterobilayer

TL;DR

This study combines theoretical and experimental approaches to understand and control impurity-bound interlayer excitonic complexes in a MoSe2/WSe2 heterostructure, revealing tunable emission properties and extended lifetimes for potential optoelectronic applications.

Contribution

It provides new insights into impurity-bound interlayer excitonic complexes and demonstrates electrostatic control over their populations and emission characteristics.

Findings

Control of neutral and charged complexes via electrostatic gating

Emission energy tuning larger than linewidth

Microsecond-scale exciton lifetimes achieved

Abstract

Due to their unique two-dimensional nature, charge carriers in semiconducting transition metal dichalcogenides (TMDs) exhibit strong unscreened Coulomb interactions and sensitivity to defects and impurities. The versatility of van der Waals layer stacking allows spatially separating electrons and holes between different TMD layers with staggered band structure, yielding interlayer few-body excitonic complexes whose nature is still debated. Here we combine quantum Monte Carlo calculations with spectrally and temporally resolved photoluminescence measurements on a top- and bottom-gated MoSe2/WSe2 heterostructure, and identify the emitters as impurity-bound interlayer excitonic complexes. Using independent electrostatic control of doping and out-of-plane electric field, we demonstrate control of the relative populations of neutral and charged complexes, their emission energies on a scale larger than their linewidth, and an increase of their lifetime into the microsecond regime. This work unveils new physics of confined carriers and is key to the development of novel optoelectronics applications.