Dipole-active vibrations confined in InP quantum dots

Dipole-active optical phonons confined in nearly spherical InP quantum dots (QDs) were studied theoretically and experimentally. Spatial quantization of the phonon modes in an InP QD was considered theoretically by solving the coupled continuous equation of motion and Poisson equation. It is shown that, when the Fröhlich frequency falls into the gap between the bulk LO and TO phonon bands, a gap mode appears, which contains most of the dipole oscillator strength. Accordingly, the shape of the far-infrared (FIR) absorption spectra does not change with the QD size. This conclusion has been confirmed by our experimental FIR spectroscopy studies on films of InP QDs prepared by colloidal synthesis. © 2002 Elsevier Science B.V. All rights reserved.