Electric-Field-Driven Trion Drift and Funneling in MoSe₂ Monolayer

Abstract

Excitons, electron–hole pairs in semiconductors, can be utilized as information carriers with a spin or valley degree of freedom. However, manipulation of excitons’ motion is challenging because of their charge-neutral characteristic and short recombination lifetimes. Here we demonstrate electric-field-driven drift and funneling of charged excitons (i.e., trions) toward the center of a MoSe2 monolayer. Using a simple bottom-gate device, we control the electric fields in the vicinity of the suspended monolayer, which increases the trion density and pulls down the layer. We observe that locally excited trions are subjected to electric force and, consequently, drift toward the center of the stretched layer. The exerting electric force on the trion is estimated to be 102–104 times stronger than the strain-induced force in the stretched monolayer, leading to the successful observation of trion drift under continuous-wave excitation. Our findings provide a new route for manipulating trions and achieving new types of optoelectronic devices.

Recent progress of exciton transport in two-dimensional semiconductors

“…The generation of strain-gradient leads to the local modification of the exciton density, as the exciton current flows toward a low bandgap energy. Therefore, various straingradient geometries have been suggested for the specific applications, such as harvesting the photon energy as a form of excitons and controlling the exciton current for the exciton integrated circuits [19,60,61,[65][66][67].…”

Nanoscale Manipulation of Exciton–Trion Interconversion in a MoSe2 Monolayer via Tip-Enhanced Cavity-Spectroscopy

“…Recently, the phenomenon of exciton-to-trion conversion in 2D semiconductors has attracted significant attention. − Trions offer distinct advantages over neutral excitons for optoelectronic device applications. Trions are responsive to external bias, enabling electrical control over their spatial distribution, a feature that can be harnessed in the development of trion-based integrated circuits. − Additionally, trions have relatively shorter lifetimes and lower binding energies compared to excitons, making them conducive to the development of highly efficient photovoltaics, such as trion-based photocurrent devices and solar cells. − To enhance the rate of exciton-to-trion conversion and improve the performance of trionic devices, plasmonic nanostructures are considered an ideal platform. ,, Plasmonic structures can induce hot electron generation, facilitate electron funneling, and reduce trion lifetimes, thus enhancing the functionality, selectivity, and sensitivity of such devices. ,, …”