Optical properties of self-assembled InAs quantum dots grown on InAlAs/InP(001)
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Optical properties of self-assembled InAs quantum dots grown on InAlAs/InP(001) B. Salem, T. Benyattou, G. Guillot and G. Bremond INSA de Lyon, LPM (UMR 5511 CNRS), 69621 Villeurbanne, France. J. Brault and M. Gendry Ecole Centrale de Lyon, LEOM (UMR 5512 CNRS), 69134 Ecully, France.
ABSTRACT Self-organized InAs quantum islands (QIs) were grown in the Stranski-Krastanov regime, by solid source molecular beam epitaxy (SSMBE), on In0.52Al0.48As layer lattice matched to InP(001) substrate. The growth parameters are chosen to produce dot shaped InAs islands as indicated by the photoluminescence (PL) linear polarization which is about 9%. The PL spectrum reveals several resolvable components. PL versus power excitation and photoluminescence excitation (PLE) measurements show clearly that this multi-component spectrum is related to emission from transitions associated to fundamental and related excited states of quantum dots (QDs) having monolayer-height fluctuations. The integrated PL intensities have been measured as a function of temperature in the 8-300 K range. The PL intensity measured at 300K is only 8 times lower than at 8 K, indicating good carrier confinement in these InAs/InAlAs QDs. An enhancement of the PL intensity in the 8-90 K temperature range has been tentatively attributed to the exciton dissociation from the InAlAs barriers which then recombine radiatively in the InAs QDs.
INTRODUCTION Up to date, an extensive amount of work has been dedicated to understanding and controlling the formation of self-assembled nanostructures by the Stranski-Krastanov growth mode, because this method today appears to be the most promising one to make quantum dots or quantum wires. For the highly mismatched system (Ga)InAs/GaAs [1,2] (mismatch up to 7%), it has led to novel quantum dot lasers [3] and photodetectors [4,5]. The InAs/InP system (mismatch ~ 3%) has also attracted considerable interest for laser sources at 1,55 µm [6-8]. Moreover, because the lateral quantum confinement in InAs islands in InAlAs matrix latticematched to an InP substrate [9-11] allows huge normal-incidence intraband absorption [12], novel quantum dot infrared photodetectors can be realized [13]. Until now, however, lasers
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based on QDs have not reached the theoretical prediction, because of the large dispersion of the dot size (≥ 10%). Moreover, the luminescence is frequently quenched at a temperature lower then 300 K. So, to make the QD-based devices work at room temperature, it is essential to investigate the temperature dependence of the photoluminescence from QDs. In this paper, we report on the electronic state spectroscopy and on the temperature dependent photoluminescence (PL) properties of self-organized InAs QDs on InAlAs/InP(001) emitting around 1.5 µm at 300 K. EXPERIMENT The samples investigated in this study were grown at 525°C by solid-source molecular beam epitaxy (SSMBE) on semi-insulating InP(001) substrate. After thermal desorption at 565 °C of the InP native oxide, a 400 nm In0.52Al0.48As buffer layer, lattic
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