The effect of ion irradiation on dephasing of coherent optical phonons in GaP

TL;DR

This study demonstrates that introducing defects via Ga-ion irradiation in GaP significantly prolongs the dephasing time of coherent optical phonons, likely due to suppressed electron-phonon scattering, as measured by femtosecond pump-probe spectroscopy.

Contribution

It reveals that ion irradiation can be used to control phonon dephasing times in GaP by defect engineering, a novel approach in phonon dynamics manipulation.

Findings

Dephasing time increased from 8.3 ps to 9.1 ps after ion irradiation.

Defect-induced deep levels suppress electron-phonon scattering.

Ion dose of 10$^{13}$/cm$^{2}$ yields optimal dephasing time.

Abstract

The dephasing of coherent longitudinal optical (LO) phonons in ion-irradiated GaP has been investigated with a femtosecond pump-probe technique based on electro-optic sampling. The dephasing time of the coherent LO phonon is found to be dramatically prolonged by the introduction of a small amount of defects by means of Ga-ion irradiation. The maximum dephasing time observed at room temperature is 9.1 ps at a Ga$^{+}$ ion dose of 10$^{13}$/cm$^{2}$, which is significantly longer than the value of 8.3 ps for GaP before ion irradiation. The longer dephasing time is explained in terms of the suppression of electron-LO-phonon scattering by the presence of defect-induced deep levels.