Exciton kinetics and luminescence in disordered In _x Ga _{1− x} P/GaAs quantum wells

Abstract

Continuous wave and time-resolved photoluminescence studies as a function of temperature have been performed on disordered In x Ga 1Àx P/GaAs quantum wells. Simulations of stationary and transient spectra, by using a two-exciton kinetic model, allow the observation of a red shift of the effective mobility edge when temperature increases. From the temperature dependence of the radiative lifetime it can be also deduced that independent localization of electrons and holes seems to be the most likely mechanism for exciton localization in our samples. On the other hand, values ranging from 0.8 to 5.6 ps have been obtained for the radiative lifetime at k k = 0. . The co-existence of localized and free excitons reflected in the two-class exciton kinetic model presented in a previous work [3] seems to describe the experimental results obtained by continuous-wave-(PL) and time-resolved-photoluminescence (TRPL) measurements as a function of temperature in In x Ga 1Àx P/GaAs quantum wells. An effective mobility edge (E ME ) defined by a Fermi function was introduced in that model. In this paper, we present an study of the variation of E ME when temperature increases and, by considering two limiting cases, we try to make a deeper view inside of the exciton in-plane localization nature.

Exciton recombination dynamics inInAs∕InPself-assembled quantum wires

“…Secondly, in order to better describe the free and localized exciton dynamics, we prefer to use here a simple kinetic model, instead of a more complicated one based on the existence of a mobility edge at certain energy within the PL band, 4 as we made in previous work for explaining exciton localization in InGaP / GaAs QWs. 5 Our model is based on a three energy level system: one for the InP barrier and the other two for the free and localized exciton states ͑similar to the model proposed in Ref. 10͒, which is depicted as an inset in Fig.…”

“…Localization traps for excitons are associated to local potential fluctuations due to well width or alloy composition fluctuations. 4,5 In the limit situation of excitons localized in quantum boxes, a negligible variation with temperature of their radiative exciton lifetime is expected. 6 Less work has been devoted to the exciton dynamics as a function of temperature in QWRs, where excitons can be localized at local potential variations due to wire height ͑more important͒ and width fluctuations.…”

Oscillator strength reduction induced by external electric fields in self-assembled quantum dots and rings

“…In this case, the broad PL band corresponds to a broad distribution of QDs with a high areal density ͑typically above 5 ϫ 10 10 cm −2 ͒, as it has been reported in previous studies of similar intrinsic samples. 24 Both samples have been characterized monitoring the PL and PC signal under different bias conditions. The spectra were measured as a function of the external voltage illuminating the sample at the GaAs band edge to create electronhole pairs only in the vicinity of the nanostructures.…”