MBE growth of InAs/GaAs quantum dots on sintered porous silicon substrates with high optical quality in the 1.3 μm band (original) (raw)
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Towards InAs/InGaAs/GaAs Quantum Dot Solar Cells Directly Grown on Si Substrate
Materials, 2015
This paper reports on an initial assessment of the direct growth of In(Ga)As/GaAs quantum dots (QDs) solar cells on nanostructured surface Si substrate by molecular beam epitaxy (MBE). The effect of inserting 40 InAs/InGaAs/GaAs QDs layers in the intrinsic region of the heterojunction pin-GaAs/n +-Si was evaluated using photocurrent spectroscopy in comparison with pin-GaAs/n +-Si and pin-GaAs/GaAs without QDs. The results reveal the clear contribution of the QDs layers to the improvement of the spectral response up to 1200 nm. The novel structure has been studied by X ray diffraction (XRD), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). These results provide considerable insights into low cost III-V material-based solar cells.
Article Towards InAs/InGaAs/GaAs Quantum Dot Solar Cells Directly Grown on Si Substrate
2016
This paper reports on an initial assessment of the direct growth of In(Ga)As/GaAs quantum dots (QDs) solar cells on nanostructured surface Si substrate by molecular beam epitaxy (MBE). The effect of inserting 40 InAs/InGaAs/GaAs QDs layers in the intrinsic region of the heterojunction pin-GaAs/n +-Si was evaluated using photocurrent spectroscopy in comparison with pin-GaAs/n +-Si and pin-GaAs/GaAs without QDs. The results reveal the clear contribution of the QDs layers to the improvement of the spectral response up to 1200 nm. The novel structure has been studied by X ray diffraction (XRD), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). These results provide considerable insights into low cost III-V material-based solar cells.
Journal of Applied Physics
InAs quantum-dot structures were grown using a GaAs 1-x Sb x matrix on a GaAs(001) substrate. The use of GaAs 1-x Sb x for the buffer and cap layers effectively suppressed coalescence between dots and significantly increased the dot density. The highest density (~ 3.5×10 11 /cm 2) was obtained for a nominal 3.0 monolayer deposition of InAs with an Sb composition of x = 13 % to 14 % in the GaAs 1-x Sb x matrix. When the Sb composition was increased to 18 %, the resulting large photoluminescent red shift (~90 meV) indicated the release of compressive strain inside the quantum dots. For x > 13 %, we observed a significant decrease in photoluminescence intensity and an increase in the carrier lifetime (≥ 4.0 ns). This is attributed to the type-II band alignment between the quantum dots and matrix material.
Chemical beam epitaxy growth and optimization of InAs/GaAs quantum dot multilayers
Journal of Crystal Growth, 2013
This paper reports on an in-situ growth process used to optimize InAs/GaAs quantum dot (QD) multilayer structures grown on (001) GaAs substrate by chemical beam epitaxy (CBE). Defects related to the incoherently relaxed InAs clusters are found to alter the QD nucleation mechanism on the subsequent layers, leading to reduced QD density and photoluminescence intensity. The formation of poor crystalline quality clusters is avoided by growing the GaAs spacer layers in a two-step process. The technique consists in covering the InAs QD layer with a 10 nm-thick GaAs layer grown at 465 1C, and then removing the excess indium contained in the uncapped portion of the clusters by increasing the temperature to 565 1C for 10 min before the deposition of the remaining GaAs spacer layer. Morphological investigation shows that the QD density and size distribution obtained in the first layer are preserved up to the tenth layer. The QD integrated photoluminescence intensity is found to increase linearly with the number of stacked layers. These results are very promising for chemical beam growth of high performance intermediate-band solar cells.
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
Journal of Luminescence, 2012
We have investigated the optical properties of InAs/GaAs (1 1 3)A quantum dots grown by molecular beam epitaxy (MBE) with different growth rates by photoluminescence spectroscopy (PL) as a function of the excitation density and the sample temperature (10-300 K). Reflection high-energy electron diffraction (RHEED) is used to investigate the formation process of InAs quantum dots (QDs). A redshift of the InAs QDs PL band emission was observed when the growth rate was increased. This result was explained by the increase of the InAs quantum dot size with increasing growth rate. A significant redshift was observed when the arsenic flux was decreased. The evolution of the PL peak energy with increasing temperature has showed an S-shaped form due to the localization effects and is attributed to the efficient relaxation process of carriers in different InAs quantum dots and to the exciton transfer localized at the wetting layer.
Molecular beam epitaxial growth of interdigitated quantum dots for heterojunction solar cells
Journal of Crystal Growth, 2019
Interdigitated quantum dots, which are multiple stacks of type-I InAs/GaAs quantum dots and type-II GaSb/GaAs quantum dots, are grown using molecular beam epitaxy. By incorporating the interdigitated quantum dots into a p-in AlGaAs/GaAs heterojunction solar cell structure, we demonstrate a photovoltaic effect with a 20.6% improvement in open-circuit voltage, when compared to that of another cell incorporating the same quantum dots but with a p-in GaAs homojunction architecture. A transmission electron microscopy is performed to analyze strain-induced defects created in the multi-stack quantum dot structures. The heterojunction solar cell incorporating the interdigitated quantum dots realized in this work would find potential applications in highefficiency single-junction intermediate band solar cells operating under concentrated sunlight.
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.
2011 Saudi International Electronics, Communications and Photonics Conference (SIECPC), 2011
Abstract-We demonstrate selectively-grown GaAs nano/micro structures on silicon substrates by molecular beam epitaxy. Hexagonal or rectangular shaped GaAs crystals, depending on the orientation of the silicon substrate, were formed inside the silicon-dioxide-masked nanoholes at 630°C. Clear facets, which are the low-energy {011} planes, indicate single-crystalline nature of the growth. GaAs/InAs/GaAs structure was also realized and strong photoluminescence spectra at 1200nm were observed at 80K.