Coherent acoustic phonon generation in GaAs1−xBix

We have used femtosecond laser pulses to generate coherent acoustic phonons in the dilute Bismide alloy, GaAs1−xBix. The observed oscillation periods match well with the oscillation periods calculated using the propagating strain pulse model. We attribute the generation process predominantly to electronic stress due to the absorption of the laser pulse at the surface of the GaAs1−xBix layer. Our initial estimates suggest that the incorporation of Bi in GaAs causes an enhancement of the hydrostatic deformation potential because of the resonant state in the valence band due to isolated Bi impurities