oa entifi s de
Keywords: ratu (PL) th rea ergy ina
QD confinement energy, is also observed in the evolution of the decay time with temperature and als und ll. Wh a few
Then t ompos emitting InAlAs QDs embedded in a GaAlAs matrix are desired. characteristics of zero-dimensional systems, such as extremely ut also by timee investigation of oles created in the it light, which is of the PL signal l processes in the perature depenInAlAs/GaAlAs QD ivation of excitons and their retrapping in QDs is observed, and its influence on exciton
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Solid State Com
Solid State Communications 227 (2016) 9?12http://dx.doi.org/10.1016/j.ssc.2015.11.011sharp homogeneous linewidths , invariant linewidths and 2. Material and methods
The QD sample was prepared by molecular-beam epitaxy, and is similar to previously studied samples : the growth of 0038-1098/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: ?216 23 642 756; fax: ?216 71 746 551.
E-mail address: email@example.com (A. Ben Daly).The InAlAs/GaAlAs QD system features a variety of interesting dynamics and PL spectra is discussed.or a hole in all three dimensions and which is sufficiently small to cause quantization of the carrier energy is named a quantum dot (QD).
The atomlike properties of QDs have made these nanostructures very attractive candidates for use in many quantum devices, such as single-electron devices , detectors , singlephoton sources  and spin-qubit [4,5]. Most studies so far concentrated on material systems such as InAs/GaAs and InGaAs/GaAs with emission in the infrared. For applications requiring visible emission such as high-density optical storage or display and illumination sources, shorter wavelength systems [6?8] such as redThe electronic and optical properties of the QD studied by photoluminescence (PL) techniques, b resolved PL (TRPL), which is a powerful tool for th carrier dynamics in semiconductors: electrons and h material by ultrashort laser pulses recombine and em subsequently detected; the temporal development allows one to draw conclusions about the dynamica sample. In this paper, we have investigated the tem dence of PL and TRPL spectra of a visible-emitting sample grown on a GaAs substrate. The thermal actthe size of the structure. A nanostructure that confines an electron that InAlAs QDs often display a relatively large inhomogeneous broadening (a few tens of meV) in their emission spectrum. s are commonlyPhotoluminescence
Carrier lifetime 1. Introduction
The physical properties of materi if the sizes become sufficiently sma are limited to regions smaller than quantum effects become apparent. no longer depend on the material c& 2015 Elsevier Ltd. All rights reserved. ergo dramatic changes en electrons and holes tens of nanometers, he material properties ition alone but also on lifetimes for temperatures up to the onset of thermionic emission , state-filling and excited-state emissions , distinctive carrier dynamics and phonon interactions  and spin-polarization features . Typical emission spectra from a self-assembled QD ensemble have a Gaussian distribution line shape at low excitation intensity, caused by small variations in the parameters of the different QDs probed, such as size, composition and strain [14?16], soQuantum dots detection energy.Temperature effects on the radiative rec quantum dots
A. Ben Daly a,n, F. Bernardot b,c, T. Barisien b,c, A. Lem a Laboratoire Mat?riaux, Mol?cules et Applications, Institut Pr?paratoire aux ?tudes Sci 2070 La Marsa, Tunis, Tunisia b Sorbonne Universit?s, UPMC Universit? Paris 06, UMR 7588, Institut des NanoScience c CNRS, UMR 7588, INSP, F-75005 Paris, France d Laboratoire de Photonique et Nanostructures, CNRS, UPR 20, Route de Nozay, F-91460 a r t i c l e i n f o
Received 15 August 2015
Received in revised form 3 October 2015
Accepted 15 November 2015
Available online 28 November 2015 a b s t r a c t
The influence of the tempe using photoluminescence retrapping in QDs, after a spectrumwidth, and an inc
PL signal, the activation en wetting layer (WL) determ journal homepage: wwmbination in InAlAs/GaAlAs ?tre d, M.A. Maaref a, C. Testelin b,c ques et Techniques, Universit? de Carthage, BP 51,
Paris, F-75005 Paris, France rcoussis, France re has been studied in self-assembled InAlAs/GaAlAs quantum dots (QDs) and time-resolved PL (TRPL). With increasing temperature, the exciton ermal activation, is evidenced and confirmed by a narrowing of the PL se of the PL decay time. From the temperature dependence of the integrate is estimated at 110 meV, in agreement with the electronic state in QD and te by PL spectroscopy measurements. The influence of the QD size on thelsevier.com/locate/ssc munications
In0.62Al0.38As QDs was performed on a 100 nm-thick Ga0.67Al0.33As epilayer, and was monitored by reflection high-energy electron diffraction (RHEED). The QDs were covered by a Ga0.67Al0.33As epilayer of same composition and same thickness.
Fig. 1 presents a sketch of the sample structure. The growth temperature is 560 ?C. The critical thickness at which the growth turns from two-dimensional (deposition of In0.62Al0.38As layers) to three-dimensional (appearance of In0.62Al0.38As QDs) is detected on the RHHED pattern; it is measured during the growth process at about 3.7 monolayers. During the PL and TRPL measurements, the sample was in a variable-temperature He-cryostat (4?150 K), on a cold finger. For the PL measurements, a 405 nm laser diode was used and focused on the sample in a 100 mm-diameter spot; the resulting PL was dispersed by a monochromator and detected by a silicon avalanche photodiode. (T?10 K) and high (T?100 K) temperatures are shown in Fig. 2. therefore, at elevated temperatures, carriers can escape the confined region by thermionic emission into the WL or barrier material . This important carrier-loss process is especially significant in structures with shallow barriers .