The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Mikael Syvajarvi - One of the best experts on this subject based on the ideXlab platform.
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Sublimation Growth of bulk 3c sic using 3c sic on si 1 0 0 seeding layers
Journal of Crystal Growth, 2017Co-Authors: Philipp Schuh, Mikael Syvajarvi, Michael Scholer, Martin Wilhelm, G Litrico, Marco Mauceri, Peter J WellmannAbstract:Abstract We have developed a transfer process of 3C-SiC-on-Si (1 0 0) seeding layers grown by chemical vapor deposition onto a poly- or single-crystalline SiC carrier. Applying subsequent Sublimation Growth of SiC in [1 0 0] direction resulting in large area crystals (up to ≈11 cm 2 ) with a thickness of up to approximately 850 μ m. Raman spectroscopy, Laue X-ray diffraction and electron-backscattering-diffraction revealed a high material quality in terms of single-crystallinity without secondary polytype inclusions, antiphase boundaries or double positioning grain boundaries. Defects in the bulk grown 3C-SiC, like protrusions with surrounding stressed areas, stem from the epitaxial seeding layer. The presented concept using 3C-SiC-on-Si seeding layers reveals a path for the Growth of bulk 3C-SiC crystals.
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quantitative study of the role of supersaturation during Sublimation Growth on the yield of 50 mm 3c sic
Materials Science Forum, 2015Co-Authors: Dominik Rankl, Mikael Syvajarvi, Valdas Jokubavicius, Peter J WellmannAbstract:We have investigated the Growth of 3C-SiC using Sublimation Growth in the temperature range from 1800°C to 1950°C. The supersaturation was determined using numerical modeling of the temperature field and gas phase composition by applying quasi-equilibrium thermodynamic conditions. Analysis of the 3C-SiC yield was carried out by optical microscopy, optical absorption, Raman spectroscopy and x-ray analysis. Quantitative data on supersaturation are compared with most stable 3C-SiC nucleation and Growth condition. Finally the application to large area Growth in a physical vapor transport Growth reactor is briefly addressed.
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modeling of the mass transport during homo epitaxial Growth of silicon carbide by fast Sublimation epitaxy
Materials Science Forum, 2013Co-Authors: Thomas Hupfer, Mikael Syvajarvi, Philip Hens, Valdas Jokubavicius, Michl Kaiser, Peter J WellmannAbstract:Ballistic and diffusive Growth regimes in the Fast Sublimation Growth Process of silicon carbide can be determined using suggested theoretical model for the mean free path calculations. The influences of temperature and inert gas pressure on the mass transport for the Growth of epitaxial layers were analyzed theoretically and experimentally.
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Sublimation Growth of thick freestanding 3c sic using cvd templates on silicon as seeds
Materials Letters, 2012Co-Authors: Rositsa Yakimova, Philip Hens, Valdas Jokubavicius, Rickard Liljedahl, Gunter Wagner, Peter J Wellmann, Mikael SyvajarviAbstract:Cubic silicon carbide is a promising material for medium power electronics operating at high frequencies and for the subsequent Growth of gallium nitride for more efficient light emitting diodes. We present a new approach to produce freestanding cubic silicon carbide (3C-SiC) with the ability to obtain good crystalline quality regarding increased domain size and reduced defect density. This would pave the way to achieve substrates of 3C-SiC so that the applications of cubic silicon carbide material having selectively (111) or (001) oriented surfaces can be explored. Our method is based on the combination of the chemical vapor deposition method and the fast Sublimation Growth process. Thin layers of cubic silicon carbide grown heteroepitaxially on silicon substrates are for the first time used for a subsequent Sublimation Growth step to increase layer thicknesses. We have been able to realize Growth of freestanding (001) oriented 3C-SiC substrates using Growth rates around 120 μm/h and diameters of more than 10 mm. The structural quality from XRD rocking curve measurements of (001) oriented layers shows good FWHM values down to 78 arcsec measured over an area of 1 × 2 mm2, which is a quality improvement of 2–3 times compared with other methods like CVD.
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Sublimation epitaxial Growth of hexagonal and cubic sic
Comprehensive Semiconductor Science and Technology, 2011Co-Authors: Mikael Syvajarvi, Rositsa YakimovaAbstract:Sublimation Growth is the key Growth process for silicon carbide. The advancements have come through from evolution from the first Acheson process to produce coarse crystalline silicon carbide, continued by the introduction of the Lely processes in which single-crystal silicon carbide was possible, to finally reach a modified Lely process with a seeding technique introduced by Tairov and Tsvetkov (1978), which made large-area single-crystal wafers available. This evolution created the platform for single-crystal Growth of semiconductor grade silicon carbide for electronics. Even so, the Growth is not completely understood. The polytype stability and their structural quality in bulk and epitaxial Growth still needs better understanding of the Growth processes. Here, we describe a Sublimation Growth process working at lower temperatures than the modified Lely Growth process. The quality of the material in relation to Growth mechanism and surface appearance as a consequence of step flow Growth and step bunching is described. The stability of hexagonal polytypes, and, in particular, the appearance of the cubic silicon carbide polytype is described.
Rositsa Yakimova - One of the best experts on this subject based on the ideXlab platform.
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Sublimation Growth of thick freestanding 3c sic using cvd templates on silicon as seeds
Materials Letters, 2012Co-Authors: Rositsa Yakimova, Philip Hens, Valdas Jokubavicius, Rickard Liljedahl, Gunter Wagner, Peter J Wellmann, Mikael SyvajarviAbstract:Cubic silicon carbide is a promising material for medium power electronics operating at high frequencies and for the subsequent Growth of gallium nitride for more efficient light emitting diodes. We present a new approach to produce freestanding cubic silicon carbide (3C-SiC) with the ability to obtain good crystalline quality regarding increased domain size and reduced defect density. This would pave the way to achieve substrates of 3C-SiC so that the applications of cubic silicon carbide material having selectively (111) or (001) oriented surfaces can be explored. Our method is based on the combination of the chemical vapor deposition method and the fast Sublimation Growth process. Thin layers of cubic silicon carbide grown heteroepitaxially on silicon substrates are for the first time used for a subsequent Sublimation Growth step to increase layer thicknesses. We have been able to realize Growth of freestanding (001) oriented 3C-SiC substrates using Growth rates around 120 μm/h and diameters of more than 10 mm. The structural quality from XRD rocking curve measurements of (001) oriented layers shows good FWHM values down to 78 arcsec measured over an area of 1 × 2 mm2, which is a quality improvement of 2–3 times compared with other methods like CVD.
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Sublimation epitaxial Growth of hexagonal and cubic sic
Comprehensive Semiconductor Science and Technology, 2011Co-Authors: Mikael Syvajarvi, Rositsa YakimovaAbstract:Sublimation Growth is the key Growth process for silicon carbide. The advancements have come through from evolution from the first Acheson process to produce coarse crystalline silicon carbide, continued by the introduction of the Lely processes in which single-crystal silicon carbide was possible, to finally reach a modified Lely process with a seeding technique introduced by Tairov and Tsvetkov (1978), which made large-area single-crystal wafers available. This evolution created the platform for single-crystal Growth of semiconductor grade silicon carbide for electronics. Even so, the Growth is not completely understood. The polytype stability and their structural quality in bulk and epitaxial Growth still needs better understanding of the Growth processes. Here, we describe a Sublimation Growth process working at lower temperatures than the modified Lely Growth process. The quality of the material in relation to Growth mechanism and surface appearance as a consequence of step flow Growth and step bunching is described. The stability of hexagonal polytypes, and, in particular, the appearance of the cubic silicon carbide polytype is described.
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Sublimation epitaxial Growth of hexagonal and cubic sic
Comprehensive Semiconductor Science and Technology, 2011Co-Authors: Mikael Syvajarvi, Rositsa YakimovaAbstract:Sublimation Growth is the key Growth process for silicon carbide. The advancements have come through from evolution from the first Acheson process to produce coarse crystalline silicon carbide, continued by the introduction of the Lely processes in which single-crystal silicon carbide was possible, to finally reach a modified Lely process with a seeding technique introduced by Tairov and Tsvetkov (1978), which made large-area single-crystal wafers available. This evolution created the platform for single-crystal Growth of semiconductor grade silicon carbide for electronics. Even so, the Growth is not completely understood. The polytype stability and their structural quality in bulk and epitaxial Growth still needs better understanding of the Growth processes. Here, we describe a Sublimation Growth process working at lower temperatures than the modified Lely Growth process. The quality of the material in relation to Growth mechanism and surface appearance as a consequence of step flow Growth and step bunching is described. The stability of hexagonal polytypes, and, in particular, the appearance of the cubic silicon carbide polytype is described.
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Sublimation Growth of aln crystals Growth mode and structure evolution
Journal of Crystal Growth, 2005Co-Authors: Rositsa Yakimova, Anelia Kakanakovageorgieva, Gholamreza Yazdi, Gueorgui Kostov Gueorguiev, Mikael SyvajarviAbstract:The aim of this study has been to realize Growth conditions suitable for seeded Sublimation Growth of AlN and to understand the relationship between external Growth parameters and the initial stages of Growth with respect to Growth mode and structure evolution. Close space Sublimation Growth geometry has been used in a RF-heated furnace employing high-purity graphite coated by TaC with a possibility to change the Growth environment from C- to Ta-rich. Influence of certain impurities on the initially formed crystallites with respect to their shape, size and population has been considered. It is shown that some impurity containing vapor molecules may act as transport agents and suppliers of nitrogen for the AlN Growth. SiC seeds, both bare and with MOCVD AlN buffer, have been employed. By varying the process conditions we have grown crystals with different habits, e.g. from needles, columnar- and plate-like, to freestanding quasi-bulk material. The Growth temperature ranged 1600–2000 °C whereas the optimal external nitrogen pressure varied from 200 to 700 mbar. There is a narrow parameter window in the relationship temperature–pressure for the evolution of different structural forms. Growth modes with respect to process conditions are discussed.
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Polytype stability in seeded Sublimation Growth of 4H}SiC boules
Journal of Crystal Growth, 2000Co-Authors: Rositsa Yakimova, Mikael Syvajarvi, Tihomir Iakimov, Henrik Jacobsson, R Raback, Asko Vehanen, Erik JanzénAbstract:Process conditions for stable single polytype Growth of 4H}SiC boules via a seeded Sublimation technique have been developed. Reproducible results can be obtained in a narrow temperature interval around 23503C and on the C-face of 4H}SiC seeds. Evidence is presented that during the initial stage of Growth, morphological instabilities may occur resulting in structural defects. A solution is proposed based on the experimental "ndings, i.e. the "rst regions of Growth ought to be carried out at a low supersaturation (Growth rate&100 lm/h) until a proper Growth front has developed. ( 2000 Elsevier Science B.V. All rights reserved.
Michael Dudley - One of the best experts on this subject based on the ideXlab platform.
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seeded Growth of bulk aln crystals and grain evolution in polycrystalline aln boules
Journal of Crystal Growth, 2005Co-Authors: Michael Dudley, Vladimir Noveski, R Schlesser, Balaji Raghothamachar, S Mahajan, Stephen P Beaudoin, Zlatko SitarAbstract:Abstract Large AlN crystals were grown by powder Sublimation in a nitrogen atmosphere at low supersaturation and Growth rates of 0.1–0.3 mm/h. The starting deposition surface was a sintered TaC disc. An appropriate adjustment of the system pressure and source-seed temperature gradient during the early stages of Growth allowed epitaxial re-Growth on AlN seeds that had been exposed to air. Single-crystalline AlN grains of 1 cm in size were achieved through multiple Sublimation Growth runs conducted at P = 500 Torr and Growth temperatures of 2050–2150 °C. Elemental analysis of impurities in the grown AlN boules confirmed low oxygen contamination levels of ∼10 19 /cm 3 . No discontinuities were introduced in the structural defect distribution in the individual single-crystalline grains by the multiple re-Growth steps. Absence of preferred Growth directions of grains suggest the epitaxial re-Growth process is suitable for seeded single-crystal Growth in any orientation.
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Growth kinetics and thermal stress in the Sublimation Growth of silicon carbide
Crystal Growth & Design, 2002Co-Authors: Hui Zhang, V L K Prasad, Michael DudleyAbstract:The productivity and quality of SiC bulk crystal grown from vapor phase depend strongly on the temperature distribution in a SiC Growth chamber. An analytical formulation is proposed to correlate the Growth rate with process parameters such as pressure, temperature, and temperature gradient. A Growth kinetic model is also developed to predict the Growth rate and examine the transport effects on the Growth rate and dislocation formation. Simulation and analytical results show that the Growth rate increases when the Growth temperature increases, argon pressure decreases, and/or the temperature gradient between the source and seed increases. An anisotropic thermoelastic stress model is proposed to study the influence of thermal stress on dislocation density. The method to attach the seed is observed to play an important role in stress distribution in an as-grown silicon carbide ingot.
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hexagonal voids and the formation of micropipes during sic Sublimation Growth
Journal of Applied Physics, 2001Co-Authors: Thomas A Kuhr, Edward K Sanchez, M Skowronski, William M Vetter, Michael DudleyAbstract:Hexagonal voids observed in Sublimation grown SiC boules were examined using optical microscopy, atomic force microscopy (AFM), scanning electron microscopy, KOH etching, and synchrotron white-beam x-ray topography. Voids formed at imperfections in the attachment layer between the seed and crucible cap. They are platelet-like in shape with lateral sizes between 50 and 750 μm and thickness along the c axis between 5 and 25 μm. Growth steps were observed on the void facets closest to the seed and evaporation steps were observed on void facets closest to the Growth surface, providing evidence for void movement during crystal Growth. AFM images revealed that Growth steps nucleate at a void sidewall, flow across the bottom of the void, and terminate in a trench-like depression. KOH etching of waters between the void and seed revealed dislocations lining up along the trace of the void path, often with higher densities corresponding to the location of the trench. X-ray topographs showed a random distribution of ...
Hui Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of thermal environment evolution on aln bulk Sublimation crystal Growth
Journal of Crystal Growth, 2007Co-Authors: D Cai, Hui Zhang, R Schlesser, Lili Zheng, D Zhuang, Z G Herro, Zlatko SitarAbstract:To obtain a large and thick AlN single crystal during Sublimation Growth, it is very important to maintain the thermal environment suitable for Growth inside the crucible during a long period of time (>50 h). In this paper, an in-house developed integrated model capable of describing inductive, radiative and conductive heat transfer will be used to simulate the transient behavior of thermal environment inside the crucible during a 40-h experiment Growth. Effects of graphite insulation degradation on temperature distribution inside the crucible will be investigated. Simulation results will be compared with the experimental data to study the effects of the insulation degradation-induced particle deposition, geometric variation of source material and crystal size enlargement on the temperature distribution in the crucible and the Growth rate. The relationship between graphite insulation degradation and power input change of the induction-heated system will be established. The evolution of temperature difference between the source material and crystal, which is the driving force for Growth, will be presented. This study will also provide the explanation of mechanism underling substantial reduction of Growth rate after a long experiment run.
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increase of sic Sublimation Growth rate by optimizing of powder packaging
Journal of Crystal Growth, 2007Co-Authors: Xiaolin Wang, D Cai, Hui ZhangAbstract:In this paper, a comprehensive model for silicon carbide (SiC) Sublimation crystal Growth considering powder packaging is presented. This model is based on heat and mass transfer of porous powder charge with different sizes of the particle and accounts for induction heating, powder charge Sublimation, vapor transport, and porosity evolution in a SiC Sublimation crystal Growth system. The mechanism of vapor transport is proposed by introducing a driving force arising from temperature difference between powder charge and seed in the Growth system. Powder porosity evolution and Sublimation rate variations are predicted based on vapor transport mechanism. Effects of powder geometry, such as particle sizes, volume and size ratios of different particles, and driving forces on the Sublimation rate are studied. In addition, simulation results for powder Sublimation with and without a central hole are presented. The results indicate that the Sublimation rate can be increased by optimizing the powder packaging, or by creating a hole in the center of packed powder.
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a novel method to increase the Growth rate in Sublimation crystal Growth of advanced materials
International Journal of Heat and Mass Transfer, 2007Co-Authors: Xiaolin Wang, D Cai, Hui ZhangAbstract:Sublimation crystal Growth technique is widely used for the Growth of optoelectronic materials, such as aluminum nitride (AlN). In this paper, an integrated model is developed to study the effects of powder geometry on crystal Growth rate whereas induction heating, powder charge Sublimation, vapor transport, and porosity evolution are considered. The mechanism of vapor transport is proposed by introducing a driving force arising from the temperature difference in AlN Sublimation Growth system. Powder porosity evolution and Sublimation rate variation are predicted based on the vapor transport mechanism. In addition, a new method by optimizing the initial powder porosity and creating holes in the packed powder is proposed to increase the crystal Growth rate. Simulation results for the Sublimation of powder with and without central hole are presented. It is found that the powder Sublimation rate is higher when hole is present. This is also validated experimentally. Effects of initial porosity, particle size and driving force on the Sublimation rate are also studied. Finally, the powder geometry is optimized based on numerical simulations. The findings from this investigation can also be applied to SiC since SiC Sublimation Growth is similar to AlN.
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integrated process modeling and experimental validation of silicon carbide Sublimation Growth
Journal of Crystal Growth, 2003Co-Authors: Hui Zhang, Marek SkowronskiAbstract:A model that integrates heat and mass transfer, Growth kinetics, anisotropic thermal stresses is developed to predict the global temperature distribution, Growth rate and dislocation distribution. The simulated temperature and Growth rate are compared with the experimental measurements. The time-depending Growth process, e.g., the variations of the Growth rate, the Growth interface shape, and the thermal stresses with time in the growing crystal are studied using the integrated model. The resolved shear stress and the von Mises stress are used to predict the dislocation density. The effects of geometric configuration and design parameters on the Growth of crystal are also discussed.
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Growth kinetics and thermal stress in the Sublimation Growth of silicon carbide
Crystal Growth & Design, 2002Co-Authors: Hui Zhang, V L K Prasad, Michael DudleyAbstract:The productivity and quality of SiC bulk crystal grown from vapor phase depend strongly on the temperature distribution in a SiC Growth chamber. An analytical formulation is proposed to correlate the Growth rate with process parameters such as pressure, temperature, and temperature gradient. A Growth kinetic model is also developed to predict the Growth rate and examine the transport effects on the Growth rate and dislocation formation. Simulation and analytical results show that the Growth rate increases when the Growth temperature increases, argon pressure decreases, and/or the temperature gradient between the source and seed increases. An anisotropic thermoelastic stress model is proposed to study the influence of thermal stress on dislocation density. The method to attach the seed is observed to play an important role in stress distribution in an as-grown silicon carbide ingot.
Philip Hens - One of the best experts on this subject based on the ideXlab platform.
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modeling of the mass transport during homo epitaxial Growth of silicon carbide by fast Sublimation epitaxy
Materials Science Forum, 2013Co-Authors: Thomas Hupfer, Mikael Syvajarvi, Philip Hens, Valdas Jokubavicius, Michl Kaiser, Peter J WellmannAbstract:Ballistic and diffusive Growth regimes in the Fast Sublimation Growth Process of silicon carbide can be determined using suggested theoretical model for the mean free path calculations. The influences of temperature and inert gas pressure on the mass transport for the Growth of epitaxial layers were analyzed theoretically and experimentally.
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Sublimation Growth of thick freestanding 3c sic using cvd templates on silicon as seeds
Materials Letters, 2012Co-Authors: Rositsa Yakimova, Philip Hens, Valdas Jokubavicius, Rickard Liljedahl, Gunter Wagner, Peter J Wellmann, Mikael SyvajarviAbstract:Cubic silicon carbide is a promising material for medium power electronics operating at high frequencies and for the subsequent Growth of gallium nitride for more efficient light emitting diodes. We present a new approach to produce freestanding cubic silicon carbide (3C-SiC) with the ability to obtain good crystalline quality regarding increased domain size and reduced defect density. This would pave the way to achieve substrates of 3C-SiC so that the applications of cubic silicon carbide material having selectively (111) or (001) oriented surfaces can be explored. Our method is based on the combination of the chemical vapor deposition method and the fast Sublimation Growth process. Thin layers of cubic silicon carbide grown heteroepitaxially on silicon substrates are for the first time used for a subsequent Sublimation Growth step to increase layer thicknesses. We have been able to realize Growth of freestanding (001) oriented 3C-SiC substrates using Growth rates around 120 μm/h and diameters of more than 10 mm. The structural quality from XRD rocking curve measurements of (001) oriented layers shows good FWHM values down to 78 arcsec measured over an area of 1 × 2 mm2, which is a quality improvement of 2–3 times compared with other methods like CVD.
