Long coherent dynamics of localized excitons in (In,Ga)N/GaN quantum wells

TL;DR

This study investigates the long-lived coherent exciton dynamics in (In,Ga)N/GaN quantum wells, revealing strong localization effects and weak exciton-phonon interactions at cryogenic temperatures.

Contribution

It provides detailed measurements of coherence times and linewidths, demonstrating quantum dot-like exciton localization in (In,Ga)N/GaN quantum wells.

Findings

Coherence times range from 45 to 255 ps depending on localization.

Homogeneous linewidths are between 5.2 and 29 μeV.

Weak exciton-phonon interaction observed.

Abstract

We study the coherent dynamics of localized excitons in 100-periods of 2.5 nm thick (In,Ga)N/GaN quantum wells with 7.5% indium concentration, measured with spectroscopic resolution through two-pulse and three-pulse photon echoes at the temperature of 1.5 K. A long-lived coherent exciton dynamics is observed in the (In,Ga)N quantum wells: When the laser photon energy is tuned across the 43 meV-wide inhomogeneously broadened resonance line, the coherence time T2 varies between 45 and 255 ps, increasing with stronger exciton localization. The corresponding narrow homogeneous linewidths ranging from 5.2 to 29 {\mu}eV as well as the relatively weak exciton-phonon interaction (0.8 {\mu}eV/K) confirm a strong, quantum dot-like exciton localization in a static disordered potential inside the (In,Ga)N quantum well layers.