MULTIPHONON PHOTOLUMINESCENCE AND RAMAN-SCATTERING IN SEMICONDUCTOR QUANTUM DOTS

Multiphonon optical spectra of semiconductor quantum dots, in particul ar, of nanocrystals with structure imperfections, are studied in the f ramework of a non-adiabatic approach. The phonon modes and the amplitu des of the electron-phonon interaction are found taking into account b oth electrostatic and mechanical boundary conditions, as well as the f inite number of vibrational degrees of freedom in quantum dots. Select ion rules for Raman scattering are deduced for quantum dots of semicon ductor materials with a degenerate valence band. The effects of non-ad iabaticity of the exciton-phonon system are shown to lead to a signifi cant enhancement of phonon-assisted transition probabilities and to a substantial difference of the optical spectra from the Franck-Condon p rogression. Calculated optical spectra compare well with experimental data on photoluminescence and Raman scattering in CdSe and PbS quantum dots. (C) 1998 Elsevier Science Ltd. All rights reserved.