F.V. de Sales

Carrier kinetics in quantum dots through continuous wave photoluminescence modeling: A systematic study on a sample with surface dot density gradient

A systematic study is presented of continuous wave (cw) photoluminescence (PL) of self-assembled quantum dots (QDs) grown on GaAs (001) by molecular-beam epitaxy as a function of excitation intensity and QD density. The sample used in this work was grown under nonisotropic indium flux that resulted in a QD density gradient across the sample surface ranging from 0 to 1.8×1011 cm−2. The carrier kinetics in the sample is described by a set of coupled rate equations through which the cw PL data from the GaAs barrier, wetting layer (WL), and QDs were simulated as a function of the excitation intensity and QD density. By comparing the PL data with our simulations we infer that carrier capture into the QD occurs directly from GaAs barrier. Auger and phonon-assisted carrier capture from the WL were found to give negligible contribution. With an increase of the QD density we observe an increase of the nonradiative recombination rates of the barrier and at the WL, which we tentatively correlate with the increase of...

Time-resolved measurements and spatial photoluminescence distribution in InAs/AlGaAs quantum dots

Abstract We report the results of time-integrated and time-resolved photoluminescence spectroscopy on red-emitting self-organized InAs/Al0.6Ga0.4As quantum dots with indirect barriers. Spatially resolved PL measurements confirm that carriers excited in the Al0.6Ga0.4As barriers are consistent with a carrier hopping process between dots, a result also supported by time-resolved PL experiments.

Excitation Transfer through Quantum Dots Measured by Microluminescence: Dependence on the Quantum Dot Density

In this study, spatially resolved cw photoluminescence of self-assembled InAs quantum dots (QDs) on a GaAs matrix has been observed using the microluminescence surface scan technique. A sample containing QD densities from 0 up to 1600 dots/μm 2 was investigated. It was found that the QD density has a strong influence on the diffusion process and there is evidence of two different mechanisms operating at low and high QD concentration ranges that we interpret as photon recycling and interdot carrier tunneling, respectively.

Carrier transport investigation in short-wavelength InAs/AlGaAs quantum dots

Spatially resolved photoluminescence has been used to investigate the details of the carrier capture and recombination dynamics in InAs/AlGaAs self-assembled quantum dots. The spatial PL distribution displays a Gaussian-like profile, whose width depends upon the temperature and detection energy being analyzed. The results give evidence of carrier thermalization between dots with different sizes. The effects of carrier transport in the quantum dot (QD) structure and carrier capture cannot be separated. The results can be modeled by assuming a carrier hopping process.

Photoexcited carrier diffusion in self-assembled InAs/GaAs quantum dots with different dot densities

Abstract The carrier dynamics in self-assembled InAs/GaAs quantum dots (QDs) has been investigated as a function of the lateral dot density. We investigated the influence of the QD density on the process of carrier transfer among the QDs. We have found evidence that potential barriers at the wetting layer and dot interfaces are responsible to decrease the carrier capture in low density QDs. This effect can be observed on the increased carrier transport.

Observation of the spectral dependence of the spatial photocarrier redistribution in InAs/GaAs quantum dots

Abstract In this work we have studied the behavior of the spatial photocarrier distribution in InAs/GaAs self-assembled QDs as a function of the emission energy. Our results show that the spread of this distribution presents an energy dependence very similar to the observed spectral dependence of the photoluminescence (PL) decay time obtained by time resolved experiments.

Step-Bunching Evidence in Strained InxGa1—xAs/GaAs Quantum Wells Grown on Vicinal (001) Substrates

In this study the influence of the interface morphology upon the photoluminescence of thick InGaAs/GaAs strained quantum wells has been investigated. Samples grown by molecular beam epitaxy, using GaAs (001) substrates with a miscut of 6° towards (111)A, have been studied using low temperature photoluminescence and transmission electron microscopy. The photoluminescence linewidth broadening was correlated with the interface morphology. The blueshift observed in the optical emissions of samples grown on vicinal substrate was well explained in terms of a simple model that includes indium segregation and strain modulation. Corrugation along the [110] direction, similar to tiles, was observed in the 200 and 300 A thick quantum wells grown on vicinal substrate. Such observation was taken as an indication of the presence of step bunches at the upper interface of the quantum wells.