Lifetime of sub-THz coherent acoustic phonons in a GaAs-AlAs superlattice

TL;DR

This study measures the lifetime of 340 GHz phonons in a GaAs-AlAs superlattice, distinguishing intrinsic and extrinsic relaxation mechanisms, and finds that these phonons are in a transition zone between two relaxation regimes at room temperature.

Contribution

It provides the first detailed measurement of sub-THz phonon lifetimes in a superlattice and analyzes the transition between phonon relaxation regimes.

Findings

Intrinsic lifetime at room temperature is approximately 0.95 ns.

Phonons at ~0.3 THz are in the transition zone between Akhiezer and Landau-Rumer regimes.

Comparison with bulk GaAs data supports the experimental results.

Abstract

We measure the lifetime of the zone-center 340 GHz longitudinal phonon mode in a GaAs-AlAs superlattice excited and probed with femtosecond laser pulses. By comparing measurements conducted at room temperature and liquid nitrogen temperature we separate the intrinsic (phonon-phonon scattering) and extrinsic contributions to phonon relaxation. The estimated room temperature intrinsic lifetime of 0.95 ns is compared to available calculations and experimental data for bulk GaAs. We conclude that ~0.3 THz phonons are in the transition zone between Akhiezer and Landau-Rumer regimes of phonon-phonon relaxation at room temperature.