Hot exciton transport in ZnSe quantum wells

TL;DR

This study investigates how excitons move within ZnSe quantum wells, revealing energy-dependent transport behaviors influenced by phonon interactions and defect limitations, with implications for optoelectronic device design.

Contribution

It provides direct experimental evidence of energy-dependent exciton transport and phonon interactions in ZnSe quantum wells, highlighting the role of kinetic energy in transport mechanisms.

Findings

Transport length increases with excess energy.

Periodic quenching of transport length at multiples of LO-phonon energy.

Distinction between phonon wind driven and defect-limited hot exciton transport.

Abstract

The in-plane transport of excitons in ZnSe quantum wells is investigated directly by microphotoluminescence in combination with a solid immersion lens. Due to the strong Froehlich coupling, the initial kinetic energy of the excitons is well controlled by choosing the excess energy of the excitation laser. When increasing the laser excess energy, we find a general trend of increasing transport length and more importantly a pronounced periodic quenching of the transport length when the excess energy corresponds to multiples of the LO-phonon energy. Such features show the dominant role of the kinetic energy of excitons in the transport process. Together with the excitation intensity dependence of the transport length, we distinguish the phonon wind driven transport of cold excitons and defect-limited hot exciton transport.