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Role of Sb on the vertical-alignment of type-II strain-coupled InAs/GaAsSb multi quantum dots structures
摘要： The implementation of GaAs0.8Sb0.2 as CL to obtain type-II strain-coupled InAs MQD structures has been examined and compared to similar structures without Sb or without strain coupling. First, it has been demonstrated that capping with GaAsSb prevents the formation of In-rich agglomerations that hampered the QD formation as it has been observed in the sample without Sb. Instead, it promotes the vertical alignment (VA) of almost all QDs with a high density of QD columns. Second, there is a preferential Sb accumulation over the dots together with an undulation of the growth front, contrary to the observed in the uncoupled structure. In case of a deficient covering of GaAsSb, as occurs for giant QDs, In-rich agglomerations may develop. Each VAQD column consists of a sequence of alternating quantum blocks of pyramid-shaped In(Ga)As separated by GaAsSb blocks that rest over them. These Sb-rich blocks are not homogeneous accumulating around the pyramidal apex like a collar. Between the columns, there is an impoverishment of In and Sb compared to the uncoupled sample. These columns can behave as self-aligned nanowires with type II band alignment between self-assembled InAs and GaAsSb quantum blocks that opens new opportunities for novel devices.
关键词： GaAsSb capping layer,III-V semiconductors alloys,Transmission electron microscopy,Composition distribution,Vertical aligned quantum dots
更新于2025-09-23 15:21:01
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Broad tunability of emission wavelength by strain coupled InAs/GaAs <sub/>1???x</sub> Sb <sub/>x</sub> quantum dot heterostructures
摘要： Tuning of the photoluminescence emission over a wider range of optical telecommunication wavelength (1.38 μm–1.68 μm) has been achieved by employing a GaAs1 ? xSbx capping layer to the strain coupled bilayer InAs quantum dot (QD) heterostructures. It is shown that the modulation of strain between the two dot layers through variation in Sb-content and thickness of the capping layer strongly influence the dot size. The band alignment transformation from type-I to type-II is observed for high Sb-content in the capping layers. In addition, the carrier lifetime is improved by a factor of three in the QD heterostructures having type-II band alignment. This, we believe, is of importance for optoelectronic device applications.
关键词： GaAs1 ? xSbx capping layer,carrier lifetime,optoelectronic device applications,photoluminescence emission,strain coupled bilayer InAs quantum dot,type-I to type-II band alignment,optical telecommunication wavelength
更新于2025-09-12 10:27:22
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Enhancing the performance of heterogeneously coupled InAs Stranski-Krastanov on submonolayer quantum dot heterostructures
摘要： A detail investigation on enhancing the performance of heterogeneously coupled Stranski–Krastanov (SK) on Submonolayer (SML) quantum dot (QD) heterostructure has been done in this study. Different approaches have been implemented on the heterostructures to extend the emission wavelength towards telecommunication window. Strain reducing capping layers such as InxGa1-xAs, InxAlyGa1-x-yAs and GaAs1-xSbx has been considered for optimizing the discussed SK on SML QD heterostructures. Impact of different configurations on the hydrostatic and biaxial strain profile as well as carrier localization has been examined. Furthermore, by implementing these configurations, the photoluminescence wavelength was extended from the previously reported wavelength (1.1 μm) towards the telecommunication window (1.3 μm), which would impact the growth and fabrication of different optoelectronic devices in the near future.
关键词： Strain,Hydrostatic,Capping layer,Photoluminescence,Quantum dots,Biaxial
更新于2025-09-11 14:15:04
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Effects of GaN capping layer on carrier occupation and interband transition probability of vertically coupled InGaN/GaN quantum dots
摘要： The carrier occupation and the interband transition probability of wurtzite (WZ) coupled InGaN/GaN quantum dots (QDs) were investigated as a function of the distance d between QDs in a range of 30?70?A. The light emission intensity rapidly decreases with increasing the distance d and becomes minimum near d=50?A. This can be explained by the fact that the matrix element values are significantly reduced with increasing d owing to an increase in the internal field and the quasi-Fermi-level separation shows a minimum value at d=50?A. However, the light intensity slightly begins to increase when d exceeds 50?A because the quasi-Fermi-level separation increases with increasing d. These results can be used as the design guideline of the active region in QD-based optoelectronic devices with a high efficiency.
关键词： optoelectronic devices,interband transition probability,GaN capping layer,InGaN/GaN quantum dots,carrier occupation
更新于2025-09-11 14:15:04
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Effects of growth temperature of a capping layer on excited spin properties of In <sub/>0.5</sub> Ga <sub/>0.5</sub> As quantum dots
摘要： We study effects of growth temperature of a capping layer on optical spin properties of In0.5Ga0.5As quantum dots (QDs) by photoluminescence (PL) spectroscopy including behaviors of the degree of circular polarization (CPD). The PL energy of the ground state shifts to lower energy with decreasing capping growth temperature, which is due to the increase of In composition inside QDs. The temperature dependence of PL intensity from the QD excited states shows the larger thermal activation energy with decreasing capping growth temperature, indicating the suppression of thermal escape of electrons from QDs to barriers. In addition, we observe the lower-energy shift of the CPD spectral peak, associated with decreasing PL energy, where the high CPD values can assure the high quality of these QDs grown with various capping growth temperatures.
关键词： capping layer,quantum dot,spin dynamics
更新于2025-09-11 14:15:04