Optical Properties of CdSe/ZnSe Quantum Dots bySelectively Excited Photoluminescence

摘要

We have investigated optical properties of self-assembledCdSe quantum dots (QDs) grown on ZnSe surfaces by selectively excitedphotoluminescence (PL) to understand carrier dynamics and energystructures of CdSe QDs. A contour map of PL intensity of CdSe QDsreveals that the strong and abrupt absorption edge of ZnSe barrier layer isclearly observed, and that the excitons in CdSe QDs are relaxed bymultiphonon processes which results from strong confinement ofexcitons in zero-dimensional structures. In QDs whose PL are detectedat lower detection energy, LO phonons of CdSe are used mostly in therelaxation processed of excitons, while excitons are relaxed by LOphonons of surrounding ZnSe barrier layers in QDs at higher detectionenergy. Moreover, since higher excited wave functions of CdSe QDsstrongly interact to each other, lower-detection-energy side in PLintensity are enhanced at higher excitation energy. Therefore, thedistribution curve of PL intensity related with 1LO-phonon structurerepresents real size distribution of CdSe QDs.