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1.
We report photoluminescence (PL) spectra of InP/InxGa1-xAs/InAs/InP dot-in-a-well structures grown by MOVPE, with different compositions of the ternary layer. Measurements with atomic force microscopy showed that the largest quantum dot (QD) height is obtained when the InAs QDs are grown on the InxGa1-xAs layer with a mismatch of 1000 ppm, and the height decreases as the mismatch departs from this value. PL spectra of the QDs showed an asymmetric band, which involves transitions between dot energy levels and can be deconvoluted into two peaks. The highest energy PL peak of this band was observed for the sample with the QDs grown on top of the lattice-matched InxGa1-xAs layer and it shifted to lower energies for strained samples as the degree of mismatch increased. Theoretical calculations of the energy levels of the entire structure were used to interpret the obtained PL spectra and determine the possible detection tunability range.  相似文献   

2.
We report structural and optical properties of In0.5Ga0.5As/GaAs quantum dots (QDs) in a 100 Å-thick In0.1Ga0.9As well grown by repeated depositions of InAs/GaAs short-period superlattices with atomic force microscope, transmission electron microscope (TEM) and photoluminescence (PL) measurement. The QDs in an InGaAs well grown at 510 °C were studied as a function of n repeated deposition of 1 monolayer thick InAs and 1 monolayer thick GaAs for n=5–10. The heights, widths and densities of dots are in the range of 6–22.0 nm, 40–85 nm, and 1.6–1.1×1010/cm2, respectively, as n changes from 5 to 10 with strong alignment along [1 −1 0] direction. Flat and pan-cake-like shape of the QDs in a well is found in TEM images. The bottoms of the QDs are located lower than the center of the InGaAs well. This reveals that there was intermixing—interdiffusion—of group III materials between the InGaAs QD and the InGaAs well during growth. All reported dots show strong 300 K-PL spectrum, and 1.276 μm (FWHM: 32.3 meV) of 300 K-PL peak was obtained in case of 7 periods of the QDs in a well, which is useful for the application to optical communications.  相似文献   

3.
The effect of strain accumulation in the InAs/In x Ga1−x As quantum dots (QDs) system was studied in this work. We found strain in the In x Ga1−x As layer with accumulation in the QD layer. This effect resulted in a dramatic reduction of growth-mode transition thickness of the QD layer. For InAs/In0.25Ga0.75As QDs, critical thickness is measured to be as low as 1.08 ML. The experimental results in this work highlight the importance of strain accumulation in the design and fabrication of QD-based devices with metamorphic buffer layer involved.  相似文献   

4.
The effect of strain accumulation in the InAs/In x Ga1−x As quantum dots (QDs) system was studied in this work. It was found that strain in the In x Ga1−x As layer accumulation in the QD layer. This effect resulted in a dramatic reduction of growth mode transition thickness of the QD layer. For InAs/In0.25Ga0.75As QDs, critical thickness is measured to be as low as 1.08 ML. The experimental results in this work highlight the importance of strain accumulation in the design and fabrication of QD-based devices with metamorphic buffer layer involved.  相似文献   

5.
Carrier dynamics in aligned InAs/GaAs quantum dots (QDs) grown on cross-hatched patterns induced by metastable InxGa1−xAs layers have been studied by time-resolved photoluminescence. The low-temperature carrier lifetimes were found to be of the order of 100–200 ps and determined by carrier trapping and nonradiative recombination. Comparisons with control “nonaligned” InAs QDs show remarkable differences in dependence of peak PL intensities on excitation power, and in PL decay times dependences on both temperature and excitation intensities. Possible origin of traps, which determine the carrier lifetimes, is discussed.  相似文献   

6.
The photoluminescence (PL) inhomogeneity has been studied in InAs quantum dots (QDs) embedded in the symmetric In0.15Ga0.85As/GaAs quantum wells (QWs) with QDs grown at different temperatures. It was shown that three reasons are responsible for the emission inhomogeneity in studied QD structures: (i) the high concentration of nonradiative recombination centers in the capping In0.15Ga0.85As layer at low QD growth temperatures, (ii) the QD density and size distributions for the structure with QD grown at 510 °C, (iii) the high concentration of nonradiative recombination centers in the GaAs barrier at higher QD growth temperatures.  相似文献   

7.
The effects of the top barrier and the dot density on photoluminescence (PL) of the InAs quantum dots (QDs) sandwiched by the graded InxGa1−xAs barriers grown by metal-organic vapor phase epitaxy (MOVPE) have been studied. Two emission peaks corresponding to the ground state and the 1st excited state transitions of the QD structures have been observed, which matches well to the theoretical calculation. The PL emission linewidth and intensity of the InAs QDs structure are improved by reducing the Indium/Gallium composition variation of the graded InxGa1−xAs top barrier layer of the structure. The QDs’ ground states filling excitation power depends on the crystal quality of the InGaAs barrier layer and the QD density. The extracted thermal activation energy for the QDs’ PL emission is sensitive to the QD size.  相似文献   

8.
Modulation doped Al0.3Ga0.7As/In x Ga1–x As/GaAs high electron mobility transistor structures for device application have been grown using molecular beam epitaxy. Initially the critical layer thickness for InAs mole fractions up to 0.5 was investigated. For InAs mole fractions up to 0.35 good agreement with theoretical considerations was observed. For higher InAs mole fractions disagreement occurred due to a strong decrease of the critical layer thickness. The carrier concentration for Al0.3Ga0.7As/In x Ga1–x As/GaAs high electron mobility transistor structures with a constant In x Ga1–x As quantum well width was investigated as a function of InAs mole fraction. If the In x Ga1–x As quantum well width is grown at the critical layer thickness the maximum carrier concentration is obtained for an InAs mole fraction of 0.37. A considerable higher carrier concentration in comparison to single-sided -doped structures was obtained for the structures with -doping on both sides of the In x Ga1–x As quantum well. Al0.3Ga0.7As/In x Ga1–x As/GaAs high electron mobility transistor structures with InAs mole fractions in the range 0–0.35 were fabricated for device application. For the presented field effect transistors best device performance was obtained for InAs mole fractions in the range 0.25–0.3. For the field effect transistors with an InAs mole fraction of 0.25 and a gate length of 0.15 m a f T of 115 GHz was measured.Dedicated to H.-J. Queisser on the occasion of his 60th birthday  相似文献   

9.
The paper presents the photoluminescence (PL) study of InAs quantum dots (QDs) embedded in the asymmetric GaAs/InxGa1?xAs/In0.15Ga0.85As/GaAs quantum wells (QWs) with the different compositions of capping InxGa1?xAs layers. The composition of the buffer In0.15Ga0.85As layer was the same in all studied QD structures, but the In content (parameter x) in the capping InxGa1?xAs layers varied within the range 0.10–0.25. The In concentration (x) increase in the InxGa1?xAs capping layers is accompanied by the variation non-monotonously of InAs QD emission: PL intensity and peak positions. To understand the reasons of PL variation, the PL temperature dependences and X ray diffraction (XRD) have been investigated. It was revealed that the level of elastic deformation (elastic strain) and the Ga/In interdiffusion at the InxGa1?xAs/InAs QD interface are characterized by the non-monotonous dependences versus parameter x. The physical reasons for the non-monotonous variation of the elastic strains and PL parameters in studied QD structures have been discussed.  相似文献   

10.
InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×1010 cm−2 was observed by atomic force microscopy before the capping process. The influences of GaAs, In0.53Ga0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.  相似文献   

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