Dynamics of in-plane charge separation front in 2D electron-hole gas

TL;DR

This paper investigates the long-lived in-plane charge separation in quantum well structures, revealing that slow diffusion and tunneling lead to persistent exciton emission lasting hundreds of microseconds.

Contribution

It provides both experimental and theoretical evidence for the extremely long lifetime of charge separation fronts in 2D electron-hole gases, highlighting the role of slow carrier dynamics.

Findings

Charge separation persists for hundreds of microseconds after excitation.

Long lifetime results from slow in-plane diffusion and tunneling.

Persistent exciton emission occurs at the charge boundary.

Abstract

We show both experimentally and theoretically that the recently observed optically induced in-plane charge separation in quantum well (QW) structures and the exciton ring emission pattern at this charge separation boundary have an extremely long lifetime. The oppositely charged carriers remain separated and provide a reservoir of excitons at their boundary with a persistent emission which lasts hundreds of microseconds (orders of magnitude longer than their recombination time) after the external excitation is removed. This long lifetime is due to an interplay between the slow in-plane carrier diffusion and slow carrier tunnelling perpendicular to the QW plane.