Carrier-induced coherent acoustic phonon excitation in strain engineered InAs/GaAs quantum dot clusters

Strain engineered InAs/GaAs quantum dot (QD) clusters grown on (311)B GaAs are studied by means of time-resolved differential reflection spectroscopy revealing coherent excitation of the quasilongitudinal and quasitransverse acoustic phonon modes. Photogenerated carriers which are captured within the ordered lateral QD clusters initiate coherent acoustic phonon excitation, which induces a transient modulation of the local strain-induced piezoelectric field within the QD clusters. The excited acoustic phonons modulate the optical properties of the QDs through the quantum-confined Stark effect, causing oscillations of the reflection signal. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)