Efficient generation of coherent acoustic phonons in (111) InGaAs/GaAs multiple quantum wells through piezoelectric effects.

The authors demonstrate the generation of coherent acoustic phonons in (111)-strained InGaAs/GaAs multiple quantum wells through piezoelectric coupling by an optical pump-probe technique. Dependence of the induced strain amplitude on the photocarrier density reveals that coherent acoustic phonons can be efficiently excited by the piezoelectric effect with an unscreened built-in electric field. Under high fluence excitation, the generation of coherent acoustic phonons saturates. The experimental results are supported by a macroscopic theoretical model. No backward Raman signal and no zone-folded phonon modes were observed in this low impedance-mismatch and finite-period heterostructure. [ABSTRACT FROM AUTHOR]