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Nucleation chronology and electronic properties of InAs <sub/>1-x-y</sub> Sb <sub/>x</sub> P <sub/>y</sub> graded composition quantum dots grown on an InAs(100) substrate
摘要： We provide a detailed study of nucleation process, characterization, electronic and optical properties of graded composition quantum dots (GC-QDs) grown from In-As-Sb-P composition liquid phase on an InAs(100) substrate in the Stranski-Krastanov growth mode. Our GCQDs exhibit diameters from 10 to 120 nm and heights from 2 to 20 nm with segregation profiles having a maximum Sb content of approximately 20% at the top and a maximum P content of approximately 15% at the bottom of the GCQDs so that hole confinement is expected in the upper parts of the GCQDs. Using an eight-band k · p model taking strain and built-in electrostatic potentials into account, we have computed the hole ground state energies and charge densities for a wide range of InAs1?x?ySbxPy GCQDs as close as possible to the systems observed in experiment. Finally, we have obtained an absorption spectrum for an ensemble of GCQDs by combining data from both experiment and theory. Excellent agreement between measured and simulated absorption spectra indicates that such GCQDs can be grown following a theory-guided design for application in specific devices.
关键词： absorption spectra,nucleation process,electronic properties,Semiconductor quantum dots,liquid-phase epitaxy,self-assembly
更新于2025-09-19 17:13:59
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[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Optimization of controlled two-step liquid phase crystallization of Ge-on-Si
摘要： This work presents a two-step liquid phase crystallization process for realizing large-grain epitaxial germanium (Ge) on silicon substrates. The process starts with amorphous Ge films on silicon (100) substrate which is subjected to a two-step annealing process. In the first step, films are heated to 950°C for 5 minutes, a temperature above the melting point of Ge. Next the films are allowed to cool down to 930°C and maintained at that temperature for 1 to 5 hours respectively in order to check its effect on the crystallization process. The 950°C for 5 mins and 930°C for 2 hours shows the optimum annealing conditions to achieve highly crystalline films. The surface morphologies of the annealed samples were characterized using scanning electron microscopy which shows grain sizes ranging from 2-5 μm. The crystallinity of the films was confirmed using Raman spectroscopy and x-ray diffraction (XRD) measurements. Theta/2-theta XRD measurements of samples show the peak for Ge(400) at 66.3°. The degree of grain orientations along Ge(400) plane is further evaluated using the rocking curve in XRD measurements which shows full-width at half maximum height value of 0.08° (or 288 arc sec) along this plane for the optimum two-step annealing process condition.
关键词： liquid phase epitaxy,Germanium,epitaxy,Silicon,Ge-on-Si
更新于2025-09-16 10:30:52
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Ytterbium calcium fluoride waveguide laser
摘要： Calcium fluoride is a well-known material for optical components. It is also suited for doping with rare-earth ions, e.g., ytterbium ones. Yb:CaF2 is an efficient gain medium for high-power and ultrashort-pulse bulk lasers around 1 μm. We report on the first Yb:CaF2 planar waveguide laser. High-optical-quality single-crystalline waveguiding Yb:CaF2 thin films are grown on bulk CaF2 substrates by Liquid Phase Epitaxy. The spectroscopic study indicates the predominant coordination of isolated Yb3+ ions in trigonal oxygen-assisted sites, C3v(T2). The optical gain in Yb:CaF2 waveguide is demonstrated. A 1.4 at.% Yb:CaF2 planar waveguide laser generated 114 mW at 1037 nm with a slope efficiency of 12.9%. Yb:CaF2 films are promising for power-scalable waveguide mode-locked lasers and amplifiers.
关键词： Waveguide laser,Liquid Phase Epitaxy,Optical gain,Ytterbium,Calcium fluoride
更新于2025-09-16 10:30:52
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Gallium Phosphide Solar Cell Structures with Improved Quantum Efficiencies
摘要： Gallium phosphide (GaP) solar cell structures with improved quantum efficiencies were realized using a modified liquid phase epitaxy (LPE) technique and diodes formed using semi-transparent Schottky contacts. The improvement is due to the addition of a small amount of aluminum to the gallium and phosphorus containing LPE melt. The Al reduces the background concentration of oxygen in the melt, which is known to produce deep trap states in GaP. Additionally, it was found that by depositing an aluminum (Al)-rich AlGaP layer on top of the active GaP and then selectively etching it away, the surface morphology of the active layer was significantly improved. Thus, the modified LPE technique eliminates the major problem of meniscus lines associated with the standard LPE method.
关键词： gallium phosphide,III–V semiconductors,Liquid phase epitaxy (LPE)
更新于2025-09-12 10:27:22
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GaAsSbN-based p-i-n heterostructures for solar cell applications grown by liquid-phase epitaxy
摘要： We present an original study on quaternary GaAsSbN layers and multilayer heterostructures grown by low-temperature liquid-phase epitaxy (LPE) on GaAs substrates aiming to explore their potential for photovoltaic applications. We choose Sn and Mg as suitable dopants for practical use. Our experiments on doping reproducibly show the introduction of controlled concentrations of doping impurities in the range applicable to device fabrication. High-quality n-, p- and nearly compensated GaAsSbN layers covering a large range of carrier concentrations from 1015 to 6 × 1018?cm?3 have been grown at temperatures lower than 600?°C. The successful LPE growth of p-i-n GaAs/GaAsSbN/GaAs heterostructures based on closely compensated i-GaAsSbN is demonstrated for the first time. Temperature-dependent photoluminescence and room temperature surface photovoltage contactless characterization techniques have been used for investigation of the grown structures. These measurements have revealed high optical quality with a low concentration of localized states and red photoresponse limit extended down to 1.2?eV.
关键词： doping,GaAsSbN,solar cells,surface photovoltage,photoluminescence,liquid-phase epitaxy
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Liquid Phase Epitaxy Growth, Spectroscopy and First Laser Operation of Yb <sup>3+</sup> :CaF <sub/>2</sub> Waveguides
摘要： Ytterbium-doped calcium fluoride (Yb:CaF2) is a recognized material for short-pulse power-scalable oscillators at ~1 μm [1]. It combines attractive thermo-mechanical properties of the host (thermal conductivity: 9.7 W/mK) with smooth and broad gain spectra for Yb3+ ions supporting broadband tuning of the laser emission and generation of sub-100 fs pulses in the mode-locking operation mode [1,2]. Nowadays, Yb:CaF2 crystals are widely used in high-power bulk continuous-wave (CW) and pulsed lasers and amplifiers. In the present work, we aimed to explore the potential of this material in waveguide laser geometry. Single-crystalline 1.4 at.% Yb:CaF2 thin films were grown by the Liquid Phase Epitaxy (LPE) method on bulk CaF2 substrates grown by the Czochralski method. As a solvent for the LPE growth, CaCl2 was used, Fig. 1(a). High optical quality Yb:CaF2 layers with a thickness of 27±1 μm were obtained, Fig. 1(b). The spectroscopic study indicates the predominant coordination of isolated Yb3+ ions in trigonal oxygen-assisted sites, C3v(T2), with a minor fraction of clusters contrary to bulk crystals [3], Fig. 1(c). The maximum stimulated-emission cross-section σSE is 0.70×10-20 cm2 at 974.9 nm (zero-phonon-line transition). The lifetime of Yb3+ ions is 2.10 ms. The refractive index variation due to the Yb3+ doping, ?n = nlayer – nsubstrate, was measured to be 5×10-3 at 633 nm.
关键词： waveguide laser,spectroscopy,laser operation,Liquid Phase Epitaxy,Yb:CaF2
更新于2025-09-12 10:27:22
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Mathematical Modeling of Droplet Formation, Evaporation, and Film Growth to Study Crystallite Size and Film Thickness of Spray Pyrolysis Deposited TiO<sub>2</sub> Thin Films
摘要： The pure TiO2 thin films were successfully deposited onto a glass substrate by using modified spray pyrolysis system. The TiO2 thin films were deposited at temperature 350?C using Titanium trichloride precursor solutions of concentration 0.075 M, 0.1 M, and 0.125 M. Also, TiO2 thin films with precursor solutions of concentration 0.1 M were deposited at different deposition temperature 350?C, 400?C, and 450?C. The prepared samples were further annealed at 500?C for 2 h to improve crystallinity. The XRD study revealed that the deposited TiO2 thin films were polycrystalline and showed anatase phase with pre-dominant (101) peak. The crystallite size calculated from XRD was found to increase with increase in precursor solution concentration. The mathematical model to calculate crystallite size and film thickness were developed and the predicted results were compared with experimental results. The experimentally calculated crystallite size and thickness was in good agreement with the predicted results. The details of mathematical model and calculations TiO2 thin films for were discussed in detail.
关键词： Growth,Liquid phase epitaxy,Crystallization,Titanium oxide,X-ray diffraction,Semiconducting films
更新于2025-09-09 09:28:46