Photoluminescence from low temperature grown InAs∕GaAs quantum dots (original) (raw)
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Photoluminescence from InAs Quantum Dots Buried Under Low-Temperature-Grown GaAs
physica status solidi (b), 2019
Optical and structural study of a system of InAs quantum dots (QDs) buried under low-temperature (LT) grown GaAs layers with different buffer layers in between has been performed. It has been shown that the buffer is very important for both atomic structure and electronic processes. The direct overgrowth at low temperature causes the formation of misfit dislocation and related drop of the photoluminescence (PL) intensity from the InAs QDs. The defect formation is eliminated by using either 5 nm thick GaAs or combined AlAs/GaAs buffer. Strong changes in the QD-related PL intensity and line shape are experimentally revealed in the case of thin GaAs buffer. These changes are quantitatively described in terms of electron tunneling from the InAs QDs through the GaAs barrier to the continuum of states in the LT-GaAs. When a 2.5 nm thick portion of the GaAs buffer is substituted by AlAs, the barrier becomes nontransparent for the electron tunneling from the ground states in the InAs QDs. As a result, the QD-related PL becomes much stronger and the line shape becomes similar to that from the reference sample in the photon energy range of ground state transitions.
Journal of Crystal Growth, 2004
Self-assembled InAs quantum dots (QDs) with In 0.15 Ga 0.85 As were grown by a molecular beam epitaxy and their optical properties were investigated by photoluminescence (PL) spectroscopy. For InAs QDs inserted in an asymmetric In 0.15 Ga 0.85 As quantum well, the emission peak position of QDs is 1.30 mm (0.953 eV) with narrower PL linewidth and larger energy-level spacing between the ground states and the first excited states compared to those of QDs embedded in a GaAs matrix. While the room temperature PL yield for InAs QDs in a GaAs matrix was reduced by 1/99 from that measured at 18 K, the reduction in PL yield for InAs QDs, grown on a 1 nm In 0.15 Ga 0.85 As layer, with a 6 nm In 0.15 Ga 0.85 As overgrowth layer was only 1/27. Also, using the In 0.15 Ga 0.85 As overgrowth layer significantly reduced the temperature sensitivity of the peak energy for InAs QDs. The relatively better temperature PL characteristics of the QDs with In 0.15 Ga 0.85 As, as well as the ability to control the emission peak position and the energy-level spacing are interesting and important for device applications. r
Optical properties of self-assembled InAs quantum dots on high-index GaAs substrates
Superlattices and Microstructures, 1997
In this work we have studied the optical properties of InAs quantum dots (QDs) grown by molecular-beam epitaxy on GaAs (211)A, on (n11)A/B (where n is 1, 5 and 7), and on reference (100) substrates. Investigation of orientation and polarity effects by means of photoluminescence (PL) are also presented. The PL spectra reveal interesting differences in amplitude, integral luminescence, peak position and peak shape. The PL temperature dependence indicates an additional lateral confinement on (100), (n11)B, (211)A and (111)A surfaces. Our results also show an enhancement of the QD onset thermal quenching energy by a factor of ∼ 3 for these orientations. In contrast, the structures grown on (711)A and (511)A surfaces do not exhibit QD formation.
Photoluminescence characteristics of InAs self-assembled quantum dots in InGaAs∕GaAs quantum well
Journal of Applied Physics, 2007
Three different InAs quantum dots ͑QDs͒ in an InGaAs/ GaAs quantum well were formed and investigated by time-resolved and temperature dependent photoluminescence ͑PL͒. A strong PL signal emitting at ϳ1.3 m can be obtained at room temperature with a full width at half maximum of only 28 meV. Dots-in-a-well structures result in strong stress release and large size InAs QDs which lead to narrowing and redshifting of PL emissions, enhancement of carrier migration, increasing carrier density in QDs, achievement of good PL lifetime stability on temperature, and improving the QD quality.
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.
1997
The structural and the optical propertics of lnAs layers grown on high index GaAs surfaces by molecular beam epitaxy are investigated in order to understand the formation and the self-organization of quantum dots (Ql)s) on novel index surfaces. Four different GaAs substrate orientations have been examined, namely, (111)B, (311)A, (311)B and (100). The (100) surface was used as a reference sample. STM pictures exhibit a uniform QI) coverage for all the samples with the exception of (111)B, which displays a surface characterized by very large islands and where STM pictures give no evidence of QD formation. The photoluminescence (PL) *Corresponding author. spectra of GaAs (100) and {311 } samples show typical QD features with PL peaks in the energy range 1.15-1.35eV with comparable efficiency. No significant quenching of PL up to temperatures as high as 70 K was observed. These results suggest that the high index substrates are promising candidates for production of high quality selfassembled QD materials for application to photonics. ,~i 1997 Elsevier Science Ltd.
Extremely low density self-assembled InAs/GaAs quantum dots
Chinese Optics Letters, 2008
The self-assembled InAs/GaAs quantum dots (QDs) with extremely low density of 8×10 6 cm −2 are achieved using higher growth temperature and lower InAs coverage by low-pressure metal-organic chemical vapour deposition (MOVCD). As a result of micro-photoluminescence (micro-PL), for extremely low density of 8 × 10 6 cm −2 InAs QDs in the micro-PL measurements at 10 K, only one emission peak has been achieved. It is believed that the InAs QDs have a good potential to realize single photon sources.
Research Journal of Applied Sciences, Engineering and Technology, 2013
This study presents self-assembled quantum dots structures made on GaAs substrate. The samples were grown by Molecular Beam Epitaxy (MBE) in the Stranski-Krastanow (SK) growth mode. Two types of quantum dots structures are performed under different growth conditions and are compared: the first type is composed of two structures with InAs quantum dots encapsulated with (Ga, In) (N, As) and the second one with boxes wrapped with InGaAs. The influence of encapsulation of quantum dots is highlighted and as already shown, the redshift of emission wavelength depends on nitrogen doping. Further investigations are done through the incorporation of indium and nitrogen in the quantum dots structures in order to understand their optimal doping level on electrical and optical properties. The effects of temperature, an important growth parameter, are examined through images of nanostructures obtained by Atomic Force Microscopy (AFM) and Scanning Electronic Microscopy (SEM) techniques.
Physica E-low-dimensional Systems & Nanostructures, 2010
Molecular beam epitaxy Focused ion beam Self-assembled quantum dot Electroluminescence a b s t r a c t An intentional positioning of optically active quantum dots using site-selective growth by a combination of molecular beam epitaxy (MBE) and focused ion beam (FIB) implantation in an all-ultra-high-vacuum (UHV) setup has been successfully demonstrated. A square array of periodic holes on GaAs substrate was fabricated with FIB of 30 keV Ga þ ions followed by an in situ annealing step. Subsequently, the patterned holes were overgrown with an optimized amount of InAs in order to achieve site-selective growth of the QDs on the patterned holes. Under well-optimized conditions, a selectivity of single quantum dot growth in the patterned holes of 52% was achieved. Thereafter, carrier injection and subsequent radiative recombination from the positioned InAs/GaAs self-assembled QDs was investigated by embedding the QDs in the intrinsic part of a GaAs-based p-i-n junction device. Electroluminescence spectra taken at 77 K show interband transitions up to the fifth excited state from the QDs.
The effects of rapid thermal annealing on doubled quantum dots grown by molecular beam epitaxy
Journal of Crystal Growth, 2009
The effects of different rapid thermal annealing temperatures on the optical properties of InAs double quantum dots (DQDs) grown by molecular beam epitaxy using a partial-capping-and-regrowth process have been investigated. Improvement of the material quality is indicated by enhanced photoluminescence (PL) intensity and narrower PL linewidth. The blueshift of the PL emission peak with increasing annealing temperature is due to the interdiffusion of group III atoms during the annealing process, which is confirmed by the temperature dependence of the PL peak position. Thermal quenching of the PL intensity is observed at temperature over 110 K, and the main activation energy decreases with annealing temperature, consistent with a reduced confining potential from the interdiffusion of group III atoms. All of these results are similar to those of single quantum dots reported in the literature.