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Growth of high quality AlN/sapphire templates with high growth rate using a medium-temperature layer
摘要： In this work, crack-free 3.3-μm-thick AlN ?lms with high crystalline quality and atomic smooth surfaces were achieved on sapphire substrates at a high growth rate of 2.9 μm/h. Double-axis x-ray rocking curves showed a full width at half maximum of 315 and 419 arc sec for (0002) and (101ˉ2) re?ections, respectively, corresponding to a total threading dislocation (TD) density of 9.79 × 10^8 cm^-2. Cracks were suppressed and crystalline quality was improved by introducing a medium-temperature (MT) layer. It was found that the density of both screw- and edge-type TDs could be signi?cantly reduced by introducing the MT-AlN layer under appropriate temperature. The crystalline improvement is attributed to the delayed coalescence of the AlN islands and higher probability for the annihilations of TDs by the MT-AlN layer under appropriate temperature. This method provides a promising way in growing practical thick AlN templates suitable for large-scale industrial production.
关键词： High growth rate,MOCVD,Crack-free,Medium-temperature layer,AlN
更新于2025-09-23 15:22:29
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Driving force of crystallisation based on diffusion in the boundary and the integration layers
摘要： Crystal growth rates are notoriously difficult to predict and even experimental data are often inconsistent. By allowing for mass and energy diffusion through the molecular and thermal layers surrounding a growing crystal and for the heat effect of crystallization, a new model of crystal growth from solution is proposed and applied to crystallization of potassium chloride from aqueous solution. The driving force for crystal growth was calculated using the solubility at the interface temperature in contrast to the conventional one based on bulk temperature. A positive heat effect at the crystal interface as well as the resistances to the mass and energy transfer processes to and from the crystal surface can reduce the conventional driving force for crystal growth by more than 20%.
关键词： Crystal growth rate,Boundary layer,Driving force,Mathematical modelling,Integration (Desolvation) layer
更新于2025-09-23 15:22:29
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Effect of tunnel junction grown at different growth rates on the optical properties and improved efficiency of InGaP/GaAs double-junction solar cells
摘要： The optical properties of InGaP/GaAs double-junction solar cells (DJSCs) grown by metalorganic chemical vapor deposition were investigated using temperature- and excitation power-dependent photoluminescence (PL) measurements. The InGaP/GaAs DJSC samples studied were the same structures; however, the corresponding tunnel junctions were grown at different growth rates (1.0 and 1.5 ?/s). The PL spectrum measured at 10 K for both samples exhibited a strong main peak at ~1.97 eV with a weak shoulder peak at ~1.94 eV, which could be attributed to the emissions of disordered and ordered InGaP, respectively. A PL peak located at ~1.91 eV was observed under a low excitation power, originating from the donoreacceptor pair (DAP) transition. With the increase in the temperature, the emission related to the DAP of the sample grown at a growth rate of 1.0 ?/s was found to be less dominant compared with the sample grown at a growth rate of 1.5 ?/s. The power-conversion ef?ciency of the sample grown at a growth rate of 1.0 ?/s was improved compared to that of the sample grown at a growth rate of 1.5 ?/s, owing to fewer defect states. Our results help understand the luminescence properties of InGaP/GaAs DJSCs, which could be a crucial factor in fabricating high-ef?ciency solar cells.
关键词： InGaP/GaAs,Growth rate,Photoluminescence,Double-junction solar cell
更新于2025-09-23 15:19:57
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Single Crystal Diamond Deposited by Dual Radio-Frequency Plasma Jet CVD with High Growth Rate
摘要： Single crystal diamonds were deposited on high pressure high temperature (HPHT) substrate with high growth rate, up to 18.5 μm/h, by using dual radio-frequency inductive coupled plasma jet. The methane ?ux was found to in?uence the growth rate of single crystal diamond. The reason for this might be ascribed to the electron temperature increase, raising the ?ux of methane, based on the plasma diagnosis results by optical emission spectra (OES). The results of Raman spectroscopy and the X-ray rocking-curve indicated that as-deposited diamonds are of good quality.
关键词： growth rate,single crystal diamond,methane ?ux,dual radio frequency,chemical vapor deposition (CVD),inductive coupled plasma jet
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Facile Optimization Method for the Passivation Layer Preparation in Silicon Heterojunction Solar Cell by Monitoring Its Growth Rate
摘要： Based on the passivation performance and the growth rate of the passivation layer as functions of the deposition conditions: deposition pressure, deposition power, SiH4 flow rate, and wafer temperature, a facile method was proposed to optimize the deposition condition for the passivation layer preparation during the a-Si/c-Si heterojunction solar cell fabrication. It is to monitor the growth rate R of the passivation layer and calculate its second-order derivative with regard to the corresponding deposition parameter. When the second-order derivative of R presents an extremum, the corresponding value of the deposition parameter can be determined as the optimized choice.
关键词： growth rate,passivation,heterojunction,deposition,solar cell,silicon
更新于2025-09-19 17:13:59
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Investigating the Efficiency Droop of Nitride-Based Blue LEDs with Different Quantum Barrier Growth Rates
摘要： In this study, GaN-based blue InGaN/GaN light-emitting diodes (LEDs) with di?erent growth rates of the quantum barriers were fabricated and investigated. The LEDs with quantum barriers grown with a higher growth rate exhibit a lower leakage current and less non-radiative recombination centers in the multiple quantum wells (MQWs). Therefore, the LED with a higher barrier growth rate achieves a better light output power by 18.4% at 120 mA, which is attributed to weaker indium ?uctuation e?ect in the QWs. On the other hand, the localized states created by indium ?uctuation lead to a higher local carrier density, and Auger recombination in the QWs. Thus, the e?ciency droop ratio of the LEDs with a higher barrier growth rate was only 28.6%, which was superior to that with a lower barrier growth rate (39.3%).
关键词： and growth rate,nitride-based LEDs,e?ciency droop,quantum barrier
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Noida, India (14–16 February 2019)] INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Stabilization of plane polarized Alfven waves by anomalous Doppler resonance
摘要： This work presents non-linear decay of plane polarized Alfven wave via anomalous Doppler resonance with an electron beam in a magnetized plasma. First order perturbation theory has been employed to derive the expressions for dispersion relation of Alfven waves and their growth rate. Numerical calculations have also been carried out for growth rate and unstable mode frequencies for typical plasma parameters. There exists two modes of wave propagation, one having frequency < ωci corresponds to Alfven wave, and the other has frequency approaching ωce which corresponds to electron cyclotron wave. The waves interact with the electron beam via normal and anomalous Doppler resonance. The normal resonance interaction increases the frequency of plane polarized Alfven wave but shows no growth or decay in amplitude. However, in anomalous resonance interaction the frequency remains unchanged and the wave stabilizes. The variation of frequency and growth rate with magnetic field and number density of plasma electrons is also discussed in the present paper. The phase velocity and the unstable frequency of the wave decrease with an increase in the number density of plasma electrons. The results of our work are applied to explain some of the experimental observations.
关键词： anomalous Doppler resonance,magnetized plasma,Alfven waves,growth rate,electron beam
更新于2025-09-11 14:15:04
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Start current and growth rate in Smith–Purcell free-electron laser with dielectric-loaded cylindrical grating
摘要： We present an analytic theory for Smith–Purcell device in which a cylindrical metal–dielectric grating was derived by an annular electron beam propagating along the grating axis. A dispersion relation is obtained for azimuthally symmetric modes. Also, the first-order and second-order growth rates of the modes which are in phase with the beam are compared. It is shown that the second-order growth rate gives a more accurate description of beam–wave interaction for beams with larger thicknesses, as well as grating slots, with smaller depths and greater lengths. The start current for BWO operation of the SP-FEL is presented too. The importance of the minimum value of start current is that above it, the SP-FEL will operate as an oscillator, even in the absence of external feedback. In this case, the group velocity of the synchronous evanescent wave is negative, while the electron beam travels in the forward direction. It is shown in this paper that the dielectric and grating parameters affect the value of start current. So, by changing these parameters, the minimum value for the start current can be obtained.
关键词： Smith–Purcell FEL,Beam–wave interaction,Cylindrical grating,Growth rate,Dielectric,Start current
更新于2025-09-11 14:15:04
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The Effect of Deposition Parameters on the Growth Rate of Microcrystalline Diamond Powders Synthesized by HFCVD Method
摘要： Conventional diamond powders (<10 μm) are generally produced from crushing large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, these powders are served as diamond seeds and regrown by hot ?lament chemical vapor deposition (HFCVD). Deposition parameters—such as the carbon concentration, substrate temperature, and bias current—which play a determined role in the homoepitaxial growth rate of micron diamonds, are investigated in their respective usual ranges. As shown in the experimental results, under the preconditions of maintaining the good morphology of crystals and inhibiting polycrystal growth, the growth rate of isolated diamond crystals can be controlled at 0.9 μm/h. Besides, the ?nal improved powders have a wide range of particle sizes, which could fail to meet the requirements for commercial powders without the post-process of sieving.
关键词： CVD diamond powders,grain size distribution,homoepitaxial growth rate,deposition parameters
更新于2025-09-11 14:12:44
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Toward the Understanding of KDP Crystal Surface Height Variation by a Rapid Growth Technique
摘要： Numerical simulations are performed to understand the variation of KDP crystal surface height by a rapid growth technique. The theoretical models used in numerical simulations couple the macroscopic transport of solute and impurities with the microscopic interfacial kinetics processes. Studies are specifically made to growth rate fluctuation at each growth interface subject to variations in crystal size, bulk supersaturation, rotation rate of the stirring paddle, and impurities. It is found that predicted interface moving speeds, equivalent to the growth rate, are uniformly distributed normal to each pyramidal and prismatic faces at macroscale by taking into account the interfacial kinetics process; however, they fluctuate wavily at microscale. The amplitude of growth rate fluctuation is on the order of micrometer. The fluctuation in growth rate will cause KDP crystal surface height variation and lead to the formation of micron-sized and nanosized inclusions in the crystals. Increasing crystal size and bulk supersaturation intensifies the fluctuation in the growth rate, which may reduce the quality of grown KDP crystal. Increasing paddle’s rotational speed can make the fluctuation of the growth rate decrease. The impurities influence the growth rate of the KDP prismatic face obviously. When impurities exist in solution, the growth rate of the prismatic face decreases greatly and the fluctuation of the growth rate is enhanced by 1 order of magnitude.
关键词： growth rate fluctuation,numerical simulations,surface height variation,rapid growth technique,KDP crystal,impurities
更新于2025-09-09 09:28:46