Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots (original) (raw)
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Thermal activated carrier transfer between InAs quantum dots in very low density samples
Journal of Physics: Conference Series, 2010
In this work we develop a detailed experimental study of the exciton recombination dynamics as a function of temperature on QD-ensembles and single QDs in two low density samples having 16.5 and 25 dots/!m 2 . We corroborate at the single QD level the limitation of the exciton recombination time in the smallest QDs of the distribution by thermionic emission (electron emission in transient conditions). A portion of these emitted carriers is retrapped again in other (larger) QDs, but not very distant from those emitting the carriers, because the process is limited by the diffusion length at the considered temperature.
Thermal induced carrier’s transfer in bimodal size distribution InAs/GaAs quantum dots
Results in Physics, 2018
This work reports on the investigation of the thermal induced carriers' transfer mechanism in vertically stacked bimodal size distribution InAs/GaAs quantum dots (QD). A model treating the QD as a localized states ensemble (LSE) has been employed to fit the atypical temperature dependence of the photoluminescence (PL) emission energies and linewidth. The results suggest that thermally activated carriers transfer within the large size QD family occurs through the neighboring smaller size QD as an intermediate channel before direct carriers redistribution. The obtained activation energy suggests also the possible contribution of the wetting layer (WL) continuum states as a second mediator channel for carriers transfer.
Carrier Recombination in InAs/GaAs Self-Assembled Quantum Dots under Resonant Excitation Conditions
physica status solidi (a), 2002
Resonant photoluminescence experiments have been performed on self-assembled quantum dots. The emission bands measured in the investigated samples can be deconvoluted in several Gaussian components, which could be related to different size families of dots. The experimental results reveal the importance of GaAs phonons for the carrier relaxation of excess energy, specially for the sample with low dot density. With increasing temperature, electrons from smaller dots can be activated to reach the wetting layer electron states, from which they can be trapped at larger dots (below 100 K) or escape to the GaAs barriers (above 100 K).
Materials Science and Engineering: B, 2021
Photoluminescence (PL) measurements are presented for self-assembled InAs/GaAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) at a growth temperature of 510°C. Two well-defined sub-bands were observed from the 8K-PL spectrum obtained under very low excitation density and unambiguously clarified as optical emissions from the ground state (GS) and first excited state (FES) of the dots. Temperature-dependent PL measurements were investigated in the 8-270K temperature range. Differently from the FES transition, a sigmoidal temperature-dependent variation was observed from the integrated PL intensity of the GS transition. This anomalous behavior was assigned to the carrier exchange between excited states and GS of the dots. A simple rate equation model which takes into account the effects of the thermal escape and re-trapping of photo-injected carriers was proposed to describe the temperature-dependent variation of the integrated PL intensity. A good agreement between the model simulation and the experimental results was obtained for temperatures ranging from 8 to 270K and which supports the argument for the carrier exchange between the excited states and the ground state. ⁕Corresponding author.
Crystals
Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs-i.e., the relative population of carriers between the two layers of QDs-changes with increasing excitation intensity. Temperature-dependent PL reveals unexpected non-monotonic variations in the peak wavelength and linewidth of the seed layer of QDs with temperature. The PL intensity ratio exhibits a "W" behavior with respect to the temperature due to the interplay between temperature and excitation intensity on the inter-layer carrier transfer.
Thermally activated carrier transfer and luminescence line shape in self-organized InAs quantum dots
Applied Physics Letters, 1996
We investigated the temperature dependence 10-180 K of the photoluminescence PL emission spectrum of self-organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: i quenching due to the escape of carriers from the quantum dots and ii carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20-30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands.
Temperature effects on the radiative recombination in self-assembled quantum dots
Surface Science, 1996
Several ensembles of self-assembled quantum dots (QDs) based on the AIInAs/AIGaAs and InGa~/GaAs material systems have been investigated using photoblminescence (PL), PL excitation (PLE) and time-resolved PL (TRPL). The influence of the temperature is measured by monitoring sharp spectral features (as narrow as ~90peV) obtained when probing the PL of ~nall QD ensembles (few hundreds QDs). Thermionic emission of the photocarriers out of the QD potential is found to be the dominant mechanism leading to the thermal quenching of the PL and temperature-independent linewidths are observed up to the onset of the PL quenchins_
New Journal of Physics, 2012
We investigate the photoluminescence temperature dependence of individual InAs/InGaAlAs quantum dots emitting in the optical telecommunication bands. The high-density dots are grown on InP substrates and the selection of a smaller dot number is done by the processing of suitable nanometer-sized mesas. Using ensembles of only a few dots inside such mesas, their temperature stability, inter-dot charge transfer, as well as carrier capture and escape mechanisms out of the dots are investigated systematically. This includes the discussion of the dot ensemble and individual dots. Among the single-dot properties, we investigate the transition of emission lines from zero-phonon line to acoustic phonon sideband-dominated line shape with temperature. Moreover, the presence of single recombination lines up to temperatures of about 150 K is demonstrated.
Crystals, 2018
The effects of post-growth thermal annealing of InAs QD with the high in-content strain reducing layer (SRL) on the temperature dependent PL properties have been investigated. The as-grown QD have shown an atypical behavior manifested by a sigmoidal emission energy and V-shaped linewidth evolution with temperature. These behaviors have been progressively glossed by subjecting the structure to post growth annealing at 650 • C and 750 • C for 50 s. The results are discussed in the frame of the localized states ensemble model, which reveals that carriers transfer take place by thermal activation to the continuum states of the strain-reducing layer and subsequent redistribution.
Semiconductor Science and Technology, 2006
In this paper, we report on the effects of the environment on the properties of an ensemble of InAs self-assembled quantum dots. The properties presented by the electrons confined at the dots can be tuned by adjusting some parameters of the environment. Using capacitance-voltage and photoluminescence measurements, we observed an increase in the thermal stability of zero-dimensional electron gas when the dots were grown in a period of a GaAs/AlAs superlattice. We believe that the parameter responsible for the thermal stability observed here was the increase of the electrical impedance of the device. In addition, electrical and optical measurements enabled us to study the thermal stability of electrons located at the dots grown in the GaAs bulk and in the aforementioned superlattice.