Temperature Effects in the Photoluminescence of Semiconductor Quantum Dots (Chapter 3)

Abstract

Temperature effects in the exciton photoluminescence specific to semiconductor quantum dots (QDs) are reviewed using Si QDs as an example. The processes of direct and indirect optical excitation of spatially confined excitons in quantum dots embedded in dielectric matrix are analyzed. The temperature behavior of the quantum dots photoluminescence (PL) excited by various methods was described in detail by a generalized electronic transitions scheme using different exciton relaxation models. The different types of temperature dependences were analyzed. The analytical expressions were obtained for their description, which allow one to determine the energy and kinetic characteristics of QD photoluminescence. It was found that the shape of the temperature dependence makes it possible to understand whether the process of exciton relaxation contains several different thermally activated stages or this is a simple one-stage process. The applicability of the obtained expressions for the analysis of the luminescence properties of quantum dots is demonstrated by the example of crystalline and amorphous silicon nanoclusters in silica matrix. It has been established that the quantum confinement effect of excitons in quantum dots leads to a decrease in the frequency haracteristics and thermal activation barriers for nonradiative transitions.