Optimizing the InGaAs/GaAs Quantum Dots for 1.3 μm Emission (original) (raw)
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Applied Physics A, 2005
Room temperature 1.3 µm emitting InAs quantum dots (QDs) covered by an In 0.4 Ga 0.6 As/GaAs strain reducing layer (SRL) have been fabricated by solid source molecular beam epitaxy (SSMBE) using the Stranski-Krastanov growth mode. The sample used has been investigated by temperature and excitation power dependent photoluminescence (PL), photoluminescence excitation (PLE), and time resolved photoluminescence (TRPL) experiments. Three emission peaks are apparent in the low temperature PL spectrum. We have found, through PLE measurement, a single quantum dot ground state and the corresponding first excited state with relatively large energy spacing. This attribute has been confirmed by TRPL measurements which allow comparison of the dynamics of the ground state with that of the excited states. Optical transitions related to the InGaAs quantum well have been also identified. Over the whole temperature range, the PL intensity is found to exhibit an anomalous increase with increasing temperatures up to 100 K and then followed by a drop by three orders of magnitude. Carrier's activation energy out of the quantum dots is found to be close to the energy difference between each two subsequent transition energies.
Growth and properties of InAs/InxGa1−xAs/GaAs quantum dot structures
Journal of Crystal Growth, 2008
Single-and double-layer InAs/GaAs quantum dot structures with strain-reducing layers (SRLs) were prepared by metalorganic vaporphase epitaxy using the Stranski-Krastanow growth mode. Structures were studied in-situ by reflectance anisotropy spectroscopy (RAS), and ex-situ by photoluminescence (PL). These structures, with very intense room temperature PL at wavelengths from 1.25 to 1.55 mm according to growth and structure parameters, were grown along while monitored with RAS. Strong correlation between RAS signal and PL intensity was found. Dependence of PL emission maximum position on SRL composition and capping layer thickness is shown. r
Photoreflectance spectroscopy of vertically coupled InGaAs/GaAs double quantum dots
Solid State Communications, 2001
Photore¯ectance and high excitation photoluminescence spectra have been measured at 10 K for In 0.6 Ga 0.4 As/GaAs double quantum dot structures with various thicknesses of the GaAs separating layer. Several transitions between split states, due to the dot±dot and wetting layer well±well interaction, have been observed. The transitions have been identi®ed using the results of the effective mass approximation calculations for double quantum wells and lens-shaped double quantum dots. The splitting energy of the quantum dot transitions has been obtained as function of the GaAs barrier width.
Structural and electrooptical characteristics of quantum dots emitting at 1.3 μm on gallium arsenide
IEEE Journal of Quantum Electronics, 2001
We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 m. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 m is obtained by embedding the dots in an InGaAs layer. Depending on the growth structure, dot densities of 1-6 10 10 cm 2 are obtained. High dot densities are associated with large inhomogeneous broadenings, while narrow photoluminescence (PL) linewidths are obtained in low-density samples. From time-resolved PL experiments, a long carrier lifetime of 1 8 ns is measured at room temperature, which confirms the excellent structural quality. A fast PL rise (rise = 10 2 ps) is observed at all temperatures, indicating the potential for high-speed modulation. High-efficiency light-emitting diodes (LEDs) based on these dots are demonstrated, with external quantum efficiency of 1% at room temperature. This corresponds to an estimated 13% radiative efficiency. Electroluminescence spectra under high injection allow us to determine the transition energies of excited states in the dots and bidimensional states in the adjacent InGaAs quantum well.
Superlattices and Microstructures, 2014
Photoluminescence (PL) of InAs quantum dots (QDs) embedded in the Al 0.30 Ga 0.70 As/In 0.15 Ga 0.85 As/InGaAlAs/GaAs quantum wells (QWs) have been investigated in the temperature range of 10-500 K for as grown samples and after thermal annealing at 640°C or 710°C for two hours. QD samples with the different InAlGaAs capping layers (GaAs or Al 0.1 Ga 0.75 In 0.15 As) have been studied. The higher PL intensity and lower energy of ground state (GS) emission are detected in the structure with Al 0.1 Ga 0.75 In 0.15 As layer. This QD structure in as grown state has smaller PL thermal decay in comparison with this parameter in the structure with GaAs layer. The variation of PL intensities and peak positions at annealing are more essential in the QD structure with Al 0.1 Ga 0.75 In 0.15 As capping layer, apparently, due to more efficient Ga(Al)/In intermixing.
Multiexcitonic emission from single elongated InGaAs/GaAs quantum dots
Journal of Applied Physics, 2012
In this work we present both experiments and simulations of multiexcitonic emission spectra of single self-assembled elongated In 0.3 Ga 0.7 As/GaAs quantum dots. The emission spectra reveal an unusual evolution with the increased excitation power density. First, a biexciton line appears simultaneously with its low energy sideband, origin of which has already been postulated previously and related to interaction of quantum dot biexciton with excitons generated in the surrounding wetting layer. A further increase of the excitation causes a disappearance of the exciton line accompanied with a transformation of the biexciton sharp line and its side band into a redshifting broad emission band. The latter recalls a typical feature of the transition from excitonic emission into electron-hole plasma called Mott transition, which is possible to occur in wire-like structures under the conditions of very high carrier densities. However, we propose an alternative explanation and show that this behavior can be well explained based on a multilevel rate equation model indicating that such a dependence of the emission spectra is a fingerprint of a formation of multiexcitonic states. Further, we discuss the importance of various quantum system parameters as the radiative lifetimes or spectral linewidths.
Luminescence from excited states in strain-induced InxGa1-xAs quantum dots
Physical Review B, 1995
We have fabricated quantum dots by locally straining In Ga&,As quantum wells with self-organized growth of nanometer-scale InP stressors on the sample surface. The structure is completed in a single growth run using metalorganic vapor-phase epitaxy. Photoluminescence from the dots is redshifted by up to 105 meV from the quantum-well peak due to the lateral confinement of excitons. Clearly resolved luminescence peaks from three
2008
Optical properties of metalorganic vapor phase epitaxy grown InAs quantum dots in GaAs covered by thin In x Ga 1−x As strain reducing layer were studied by photomodulated reflectance and photoluminescence spectroscopy. Results show that the increasing In content in the strain reducing layer shifts the luminescence of quantum dots from 1.25 to 1.46 m and narrows the photoluminescence linewidth. To interpret photoluminescence data, we developed a simulation model of our quantum dot structure, which was calibrated using results of atomic force microscopy, photoluminescence and photoreflectance measurements. Simulations have shown that the strong photoluminescence red shift is caused both by the change of the band structure and the height of quantum dots which is significantly increasing when the In content in the strain reducing layer grows.
Applied Physics Letters, 2020
The electronic structure of strain-engineered single InGaAs/GaAs quantum dots emitting in the telecommunication O band is probed experimentally by photoluminescence excitation spectroscopy. Observed resonances can be attributed to p-shell states of individual quantum dots. The determined energy difference between s-shell and p-shell shows an inverse dependence on the emission energy. The experimental data are compared with the results of confined states calculations, where the impact of the size and composition in the investigated structures is simulated within the 8-band k•p model. On this basis, the experimental observation is attributed mainly to changes in indium content within individual quantum dots, indicating a way of engineering and selecting a desired quantum dot, whose electronic structure is the most suitable for a given nanophotonic application.