Optical properties of CdS/HgS/CdS quantum dot-quantum well structures

The optical properties of different quantum dot-quantum well (QDQW) structu res and of CdS-core dots have been studied utilizing photoluminescence (PL) , fluorescence line narrowing (FLN), photoluminescence excitation (PLE), an d double-beam PL spectroscopy. The FLN spectra of the CdS core showed reson ant Raman lines, distinct from the exciton-phonon replica. The red shift of PL from the absorption edge there "Stokes shift") and the phonon energy in the QDQW samples differ from those in the CdS core and from HgS bulk. The Stokes shift has an inversed energy dependence in one QDQW sample compared with all others. An additional, special double beam PL experiment showed an enhancement of the excitonic band as consequence of the partial quenching of the defect band, suggesting a mutual interaction between the two lumines cence events.