Decay time extension of terahertz electromagnetic waves emitted from coherent longitudinal optical phonons in GaAs epitaxial layers with the use of fast atom bombardment

We succeeded in extending the decay time of terahertz electromagnetic waves from coherent longitudinal optical (LO) phonons in GaAs epitaxial layers with the use of fast atom bombardment, a treatment method for introducing defects and/or disorders at the surface. The decay time becomes long, up to 4.81 +/- 0.15 ps, with the bombardment time of 4.0 min. This value is 2.4-times larger than the decay time of 2.04 +/- 0.04 ps of the reference sample (untreated sample). We attribute the origin of the present phenomenon to the fact that the reduction of the photogenerated carrier scattering effect on the coherent LO phonon, which is caused by the presence of the surface defects and disorders formed by the fast atom bombardment, results in the extending of the decay time of the terahertz wave from the coherent LO phonon. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement