1986 Fiscal Year Final Research Report Summary
Theoretical Study of the Growth of a Perfect GaAs Crystal by MLEC method
| Project/Area Number |
60580042
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
結晶学
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| Research Institution | Toyama University |
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Principal Investigator |
KOBAYASHI Nobuyuki Toyama University, Faculty of Engineering, 工学部, 教授 (50019204)
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| Co-Investigator(Kenkyū-buntansha) |
IWAKI Toshihiro Toyama University, Faculty of Engineering, 工学部, 講師 (90019191)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Crystal Growth / Perfect Crystal / Czochralski method / MLEC method / GaAs / Convection / Heat transfer / マランゴニ対流 |
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| Research Abstract |
The Process of the crystal growth by the LEC method is modeled and simulated. The crystal growth model includes the essential features of the method and the temperatures in the crystal and melt are obtained.
1. Temperature distribution and thermal stress in the crystal: The temperature and thermal stress in the crystal are exactly solved for a finite and semi-infinite cylinders. For a short crystal a strong stress occurs at the top center of the crystal surface and for a long crystal the maximum thermal stress occurs at the crystal periphery near the solid-liwuid interface. To find the growth direction for which the thermal stress becomes minimum, the growth direction dipendence of the thermal stress is investigated for various growth directions. Furthermore, the procedure to obtaine the dislocation array pattern from the thermal stress is postulated. After all, to obtaine a dislocation free crystal, it is necessary to reduce the thermal stress in the crystal and it will be satisfied if the heat loss from the crystal side surface is reduced.
2. Temperature distribution and fluid convection in the melt: A computer simulation code to obtaine the temperature and fluid convection under an axial magnetic field is devised. The convection in the melt is suppressed by the magnetic field. There is a possibility that the free convection doninant flow is suppressed and reversed under the crystal by the magnetic field and that the melt is occupied by a forced convection dominant flow caused by crystal rotation There is also a possibility that there exists a marangoni convection caused by a surface tension gradient near the melt-fluid boundaries. The marangoni convections are obtained for various magnetic field strengths and found that the marangoni convection has a similarity as the free convection. Finally, the crucible rotation as well as the magnetic field is also effective to suppress and to two-dimensionalise the convection in the melt.
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