Photoluminescence of InAs Self-Organized Quantum Dots Formation on InP Substrate by MOCVD (original) (raw)
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Photoluminescence evolution in InAs/InP quantum dots grown by MOVPE
Self-assembled quantum dots of InAs have been grown on InP substrates by metal-organic vapour phase epitaxy. The effect of the growth temperature and the growth rate on the morphology and the optical properties of the quantum dots is studied using atomic force microscopy and photoluminescence spectroscopy. The spectral shape of the low temperature photoluminescence depends strongly on the growth conditions. A single peak, observed at a high growth rates, develops into two o r even three distinct peaks for different samples grown at progressively lower growth rates. These findings weakly correlate with the observed size distribution of the quantum dots although the role of arsenic/phosphorous exchange at the Group-V sites may also be important. The temperature dependence of the photoluminescence spectra for the samples with a single peak is also discussed.
Self-assembling InAs and InP quantum dots for optoelectronic devices
Thin Solid Films, 2000
Stranski-Krastanov growth in molecular beam epitaxy allows the preparation of self assembling InAs and InP quantum dots on GaAs and Ga0,521no,4,P buffer layers, respectively. InAs dots in GaAs prepared by slow growth rates and low temperature overgrowth provide intense photoluminescence at the technologically important wavelength of 1.3 p,m at room temperature. Strain induced vertical alignment, size modification and material interdiffusion for stacked dot layers are studied. A blue shift of the ground state transition energy is observed for the slowly deposited stacked InAs dots. This is ascribed to enhanced strain driven intermixing in vertically aligned islands. For very small densely stacked InP and InAs dots the reduced confinement shift causes a red shift of the ground state emission. The InP quantum dots show intense and narrow photoluminescence at room temperature in the visible red spectral range. First InP/Ga0,521no,4,P quantum dot injection lasers are prepared using threefold stacked InP dots. We observe lasing at room temperature in the wavelength range between 690-705 nm depending on the size of the stacked InP dots.
Journal of Electronic Materials, 2001
We report the characteristics of InP self-assembled quantum dots embedded in In 0.5 Al 0.5 P on GaAs substrates grown by metalorganic chemical vapor deposition. The InP quantum dots show increased average dot sizes and decreased dot densities, as the growth temperature increases from 475°C to 600°C with constant growth time. Above the growth temperature of 600°C, however, dramatically smaller and densely distributed self-assembled InP quantum dots are formed. The small InP quantum dots grown at 650°C are dislocation-free "coherent" regions with an average size of ~20 nm (height) and a density of ~1.5 × 10 8 mm -2 . These InP quantum dots have a broad range of luminescence corresponding to red or orange in the visible spectrum.
First observation of 2.4 µm photoluminescence of InAsSb/InP quantum dots on InP(100) substrate
A theoretical and experimental study of the electronic properties of InAsSb quantum dots (QDs) grown on InP substrate is presented. Unstrained bulk materials present direct gap between 0.1 eV to 0.35 eV suitable for mid infrared emitters (2-5 m). However, strain and quantum confinement effects may limit the extension of the emission spectrum of these nanostructures towards the higher wavelengths. Various combinations of barrier materials are considered in the simulations. Preliminary photoluminescence spectroscopy experiments on molecular beam epitaxy (MBE) grown samples show promising results. Triple stacks of InAs QDs embedded in a GaInAsP alloy lattice matched to InP and grown by the Stranski-Krastanov mode exhibit room temperature (RT) luminescence at about 2 µm. Emission wavelengths as long as 2.4 µm have been observed at RT with a InAsSb/InGaAs/InP structure.
Cathodoluminescence imaging and spectroscopy of excited states in InAs self-assembled quantum dots
Journal of Applied Physics, 2005
We have examined state filling and thermal activation of carriers in buried InAs self-assembled quantum dots ͑SAQDs͒ with excitation-dependent cathodoluminescence ͑CL͒ imaging and spectroscopy. The InAs SAQDs were formed during molecular-beam epitaxial growth of InAs on undoped planar GaAs ͑001͒. The intensities of the ground-and excited-state transitions were analyzed as a function of temperature and excitation density to study the thermal activation and reemission of carriers. The thermal activation energies associated with the thermal quenching of the luminescence were measured for ground-and excited-state transitions of the SAQDs, as a function of excitation density. By comparing these activation energies with the ground-and excited-state transition energies, we have considered various processes that describe the reemission of carriers. Thermal quenching of the intensity of the QD ground-and first excited-state transitions at low excitations in the ϳ230-300-K temperature range is attributed to dissociation of excitons from the QD states into the InAs wetting layer. At high excitations, much lower activation energies of the ground and excited states are obtained, suggesting that thermal reemission of single holes from QD states into the GaAs matrix is responsible for the observed temperature dependence of the QD luminescence in the ϳ230-300-K temperature range. The dependence of the CL intensity of the ground-and first excited-state transition on excitation density was shown to be linear at all temperatures at low-excitation density. This result can be understood by considering that carriers escape and are recaptured as excitons or correlated electron-hole pairs. At sufficiently high excitations, state-filling and spatial smearing effects are observed together with a sublinear dependence of the CL intensity on excitation. Successive filling of the ground and excited states in adjacent groups of QDs that possess different size distributions is assumed to be the cause of the spatial smearing.
Anomalous excitation intensity dependence of photoluminescence from InAs self-assembled quantum dots
1998
ÐWe have studied photoluminescence (PL) from single InAs self-assembled quantum dots (QDs) by micro-PL measurements and, in particular, studied the excitation intensity dependence. We have found strong quenching in both the peak and integrated intensity of narrow PL lines when the excitation power was increased. This suggests that the present behavior is mainly due to the change of carrier screening and relaxation between the InAs wetting layer and InAs QDs.
Electrical properties of self-assembled InAs/InAlAs quantum dots on InP
Semiconductor Science and Technology, 2010
The characteristics of InAs self-assembled quantum dots (QDs) grown on InAlAs/InP (001) have been investigated by capacitance-voltage (C-V) measurements and deep-level transient spectroscopy (DLTS). The depth profile of the apparent electron concentration obtained by C-V measurements shows significant carrier accumulation around the position of the InAs QDs plane. In addition to the D 1-D 5 traps, which are commonly detected in InAlAs layers grown on InP by molecular beam epitaxy (MBE), DLTS investigations show three InAs-related levels located at about 76, 202 and 246 meV below the InAlAs conduction band edge. The applied field is found to significantly enhance tunnel emission processes as seen in the broadening of the peaks with increasing reverse bias. The results suggest that defects in the material barrier can enhance electron tunnelling through barriers.
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.
Journal of Physics: Conference Series, 2017
The lateral interdot coupling is investigated in high density (∼10 11 cm −2) selfassembled InAs quantum dots (QDs) grown on an InP substrate. Two types of structures are selected for this study, in which QDs are embedded into an InAlAs matrix, forming nearly twice stronger confinement for an electron and a hole than expected for an InAlGaAs counterpart. Resonantly injected low carrier population in these families of QDs gives very different spectral and temporal response in the temperature range of 5-30 K. While InAs/InAlGaAs QDs show monotonic temperature quench of photoluminescence (PL), the process seems to be ineffective in the family of InAs/InAlAs dots. Moreover, the PL decay traces for InAs/InAlGaAs QDs reveal a two-exponential decay as compared to a mono-exponential one observed for InAs/InAlAs dots. While a short decay component of ≤1.9 ns has been attributed to recombination of an electronhole pair confined in the dot, the long one of >2.4 ns, observed exclusively for InAs/InGaAlAs QDs, is attributed to recombination of spatially separated electron-hole pairs formed due to carrier exchange between adjacent dots.