共查询到18条相似文献,搜索用时 218 毫秒
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采用高压垂直温度梯度凝固法(VGF)生长了非掺、掺硫和掺铁的4 inch直径(100)InP单晶,获得的单晶的平均位错密度均小于5000 cm-2.对4 inch InP晶片上进行多点X-射线双晶衍射测试, 其(004)X-射线双晶衍射峰的半峰宽约为30弧秒且分布均匀.与液封直拉法(LEC)相比, VGF-InP单晶生长过程的温度梯度很低,导致其孪晶出现的几率显著增加.然而大量晶体生长结果表明VGF-InP晶锭上出现孪晶后,通常晶体的生长方向仍为(100)方向,这确保从生长的4 inchVGF-InP(100)晶锭上仍能获得相当数量的2~4 inch(100)晶片.由于铁在InP中的分凝系数很小,掺Fe-InP单晶VGF生长过程中容易出现组份过冷,导致多晶生长.通过控制生长温度梯度及掺铁量,可获得较高的掺铁InP单晶成晶率.对VGF-InP单晶的电学性质、位错密度及位错的分布特点、晶体完整性等进行了研究. 相似文献
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钼酸铅单晶生长及其缺陷研究 总被引:2,自引:0,他引:2
本文通过CZ法生长钼酸铅单晶,讨论了温度梯度、拉速、转速等生长参数对晶体质量的影响,分析了晶体开裂、包裹物等宏观缺陷以及位错等微观缺陷的形成机理,并从晶体形态、包裹体和位错密度变化方面探讨了晶体生长参数与晶体缺陷之间的内在关系,从而优化温度梯度等生长参数.温度梯度为20~25℃/cm,晶体转速为28r/min,拉速为1.6mm/h时,生长出的晶体形态完整,无开裂现象,晶体中无气泡包裹体,位错密度明显减小,晶体尺寸达φ40mm×70mm,无散射颗粒,在波长0.42~5.5μm范围内,平均透光率为72.6;. 相似文献
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通过对定向凝固多晶硅从凝固过程开始到冷却过程结束进行瞬态数值模拟,研究了多晶硅锭不同生长阶段的温场、热应力及位错密度的关系.模拟结果表明:在长晶及冷却过程中,位错因热应力的存在而发生运动和增殖,晶体内温度梯度是影响晶体位错密度的关键因素.高位错密度区域分布在硅锭顶部、中心部以及周边外缘.硅锭上表面由中心向外缘递减的高位错密度是由于杂质在固液界面前沿富集导致.其中最大位错密度约为2.4×104 cm-2,发生在硅锭中轴顶部;局部最大位错密度约为2.2×104 cm-2,发生在硅锭边缘底角. 相似文献
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针对泡生法蓝宝石单晶生长的不同生长阶段的温场、流场和固液界面形状进行数值模拟研究.并分析了加热器相对坩埚的轴向位置和不同生长速率对蓝宝石单晶生长的影响.结果表明:在蓝宝石单晶生长中,在靠近坩埚壁面和固液界面的熔体内,等温线密,温度梯度较大;在靠近坩埚底部的熔体内,等温线稀疏,温度梯度较小.随着晶体高度的增加,熔体对流由放肩阶段的两个涡胞变成等径阶段的一个涡胞,熔体平均温度有小幅度下降;加热器相对坩埚的轴向位置对晶体生长炉内温场和固液界面形状影响很大,随着加热器位置上移,晶体内平均温度升高,温度梯度减小;熔体内平均温度降低,温度梯度增大.同时固液界面凸度增大.随着晶体生长速率增大,固液界面凸度增大,界面更加凸向熔体. 相似文献
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声光晶体TeO2的生长及缺陷研究 总被引:2,自引:1,他引:1
本文研究了直接TeO2晶体中的主要晶体缺陷形成机理,讨论分析了T eO2单晶生长的工艺参数对晶体缺陷的影响,结果表明:晶体裂缝的主要与温度梯度有关,温度梯度大于20-25℃/cm及出现界面翻转时,易造成晶全的开裂,位错密度增加,晶体中的包裹体主要为气态包裹全,它的形成主要与籽晶的转速和晶体的提拉速率有关,转速15-18r/min,拉速0.55mm/h,固液界面微凹,可以减少晶体中的气态包裹体,晶体台阶由晶体生长过程中温度和生长速度的引起伏引起,当台阶间距较宽时,易形成包裹体。 相似文献
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Liu Juncheng 《Crystal Research and Technology》2008,43(4):396-408
A numerical simulation study was carried out for CdZnTe vertical Bridgman method crystal growth with the accelerated crucible rotation technique (ACRT). The convection, heat and mass transfer in front of the solid‐liquid interface, and their effects on the solute segregation of the grown crystal can be characterized with the following. ACRT brings about a periodic forced convection in the melt, of which the intensity and the incidence are far above the ones of the natural convection without ACRT. This forced convection is of multiformity due to the changes of the ACRT parameters. It can result in the increases of both the solid‐liquid interface concavity and the temperature gradient of the melt in front of the solid‐liquid interface, of which magnitudes vary from a little to many times as the ACRT wave parameters change. It also enhances the mass transfer in the melt in a great deal, almost results in the complete uniformity of the solute distribution in the melt. With suitable wave parameters, ACRT forced convection decreases the radial solute segregation of the crystal in a great deal, even makes it disappear completely. However, it increases both the axial solute segregation and the radial one notably with bad wave parameters. An excellent single crystal could be gotten, of which the most part is with no segregation, by adjusting both the ACRT wave parameters and the crystal growth control parameters, e.g. the initial temperature of the melt, the temperature gradient, and the crucible withdrawal rate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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《Journal of Crystal Growth》1999,196(1):62-66
A computer code for simulation of dislocation density in a bulk single crystal during liquid encapsulated Czochralski (LEC) or Czochralski (CZ) growth process. In this computer code, the shape of crystal–melt interface and the temperature in a crystal at an arbitrary time were determined by linear interpolation of the results that were discretely obtained by heat conduction analysis of a CZ single crystal growth system. A dislocation kinetics model called Haasen–Sumino model was used as a constitutive equation. In this model, creep strain rate is related to dislocation density, and this model extended to multiaxial stress state was incorporated into a finite element elastic creep analysis program for axisymmetric bodies. Dislocation density simulations were performed using this computer code for InP bulk single crystals with about 8″ in diameter. In the analysis, the effect of dopant atoms on the dislocation density was examined. In the case of a low doped InP single crystal, dislocations are distributed in the whole of the crystal. On the other hand, in the case of a highly doped InP single crystal, dislocations are localized at both the central and peripheral regions of the crystal. 相似文献
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A. N. Danilewsky A. Crll J. Tonn M. Schweizer S. Lauer K. W. Benz T. Tuomi R. Rantamki P. McNally J. Curley 《Crystal Research and Technology》2009,44(10):1109-1114
The behaviour of dislocations in GaSb crystals grown in space both from a stoichiometric melt (floating zone method, FZ) and a Bi solution (floating solution zone, FSZ) respectively, is studied. Predominantly straight 60° dislocations with Burgers vectors of the type b = a/2 <110> in (111) glide planes are identified. In the 20 mm long FZ single crystal the linear growing out of the dislocations is observed which reduces the dislocation density in the centre of the crystal to values below 300 cm–2. The Bi incorporation in the FSZ crystal results in a misfit between seed and grown crystal and in a network of misfit dislocations at the interface. Thermocapillary convection during growth as well as the surface tension may be the reasons for the presence of curved dislocations and the higher dislocation density within a 1 – 2 mm border region at the edges of both of the crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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E. V. Yakovlev V. V. Kalaev E. N. Bystrova O. V. Smirnova Yu. N. Makarov Ch. Frank‐Rotsch M. Neubert P. Rudolph 《Crystal Research and Technology》2003,38(6):506-514
The results of three‐dimensional unsteady modeling of melt turbulent convection with prediction of the crystallization front geometry in liquid encapsulated Czochralski growth of InP bulk crystals and vapor pressure controlled Czochralski growth of GaAs bulk crystals are presented. The three‐dimensional model is combined with axisymmetric calculations of heat and mass transfer in the entire furnace. A comprehensive numerical analysis using various two‐dimensional steady and three‐dimensional unsteady models is also performed to explore their possibilities in predicting the melt/crystal interface geometry. The results obtained with different numerical approaches are analyzed and compared with available experimental data. It has been found that three‐dimensional unsteady consideration of heat and mass transfer in the crystallization zone provides a good reproduction of the solidification front geometry for both GaAs and InP crystal growth. 相似文献
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The influence of convection and heat and mass transfer on the shape and position of melt/solid interfaces and on radial composition segregation is analysed numerically for the travelling heater method growth of a binary alloy in a vertical transparent ampoule. Results are presented for crystal and melt with thermophysical properties similar to CdxHg1−xTe with the assumption that the pseudobinary CdTe-HgTe phase diagram is true. The two-dimensional axisymmetric heat transfer equation, hydrodynamical equation and convective diffusion equation are included in the mathematical model. The rates of crystal growth and dissolution are supposed to be proportional to the compositional supercooling in the melt near the interfaces. It is shown for the conditions when convection is absent that the interfaces are asymmetrically positioned respectively to the heater centre line. Intensive convection makes their position more symmetrical but the length of the liquid zone greater. The flow pattern in the melt appears to be greatly influenced by solutal gravitational convection. The nonlinear dependence of the melt density on the temperature and composition are used in the model. The cases when speed of the heater is antiparallel (stable density stratification) or parallel (unstable stratification) to the vector of gravitational acceleration are considered. 相似文献
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A computer simulation is carried out to study the dopant concentration fields in the molten zone and in the growing crystal for the floating zone (FZ) growth of large (> 100 mm) Si crystals with the needle-eye technique and with feed/crystal rotation. The mathematical model developed in the previous work is used to calculate the shape of the molten zone and the velocity field in the melt. The influence of melt convection on the dopant concentration field is considered. The significance of the rotation scheme of the feed rod and crystal on the dopant distribution is investigated. The calculated dopant concentration directly at the growth interface is used to determine the normalized lateral resistivity distribution in the single crystal. The calculated resistivity distributions are compared with lateral spreading resistivity measurements in the single crystal. 相似文献
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Macro-segregation, dynamics of interface and stresses in high pressure LEC grown crystals 总被引:3,自引:0,他引:3
Y. F. Zou G. -X. Wang H. Zhang V. Prasad D. F. Bliss 《Journal of Crystal Growth》1997,180(3-4):524-533
High dislocation density and strong dopant inhomogeneities have been found in high pressure liquid-encapsulated Czochralski (HPLEC) grown crystals. The origin and underlying mechanisms of these defects are attributed to the complex nature of transport phenomena in the HPLEC system. Our integrated computer model (MASTRAPP) can simulate this process by calculating the flow and heat transfer in both the melt and the gas, and thermal-elastic stress in the crystal. In this work, this model has been further extended to investigate the development of thermal stress in the growing crystal and the redistribution of dopant in the melt. The results for InP growth show complex gas flow and heat transfer pattern in the system. Two large stress spots are predicted by the model, one at the edge of the crystal just above the encapsulant layer and the other in the top corner of the crystal. Although the stress always remains largest at the first location, its value decreases as the crystal grows, due to the enhanced cooling of the crystal. A curved crystal/melt interface is also found to introduce high thermal stresses in its vicinity, which may be dangerous because of a high temperature at the interface and thus a low strength of the crystal. The model also predicts both radial and longitudinal dopant segregation in the growing crystal, and shows that the dopant redistribution in the melt is caused by the complex flow pattern in the melt. This is the first time, that a strong radial dopant segregation has been predicted based on a comprehensive flow model for a HPLEC growth. 相似文献
18.
Takao Abe Toru Takahashi Koun Shirai 《Progress in Crystal Growth and Characterization of Materials》2019,65(1):36-46
It has been known that, in growing silicon from melts, vacancies (Vs) predominantly exist in crystals obtained by high-rate growth, while interstitial atoms (Is) predominantly exist in crystals obtained by low-rate growth. To reveal the cause, the temperature distributions in growing crystal surfaces were measured. From this result, it was presumed that the high-rate growth causes a small temperature gradient between the growth interface and the interior of the crystal; in contrast, the low-rate growth causes a large temperature gradient between the growth interface and the interior of the crystal. However, this presumption is opposite to the commonly-accepted notion in melt growth. In order to experimentally demonstrate that the low-rate growth increases the temperature gradient and consequently generates Is, crystals were filled with vacancies by the high-rate growth, and then the pulling was stopped as the extreme condition of the low-rate growth. Nevertheless, the crystals continued to grow spontaneously after the pulling was stopped. Hence, simultaneously with the pulling-stop, the temperature of the melts was increased to melt the spontaneously grown portions, so that the diameters were restored to sizes at the moment of pulling-stop. Then, the crystals were cooled as the cooling time elapsed, and the temperature gradient in the crystals was increased. By using X-ray topographs before and after oxygen precipitation in combination with a minority carrier lifetime distribution, a time-dependent change in the defect type distribution was successfully observed in a three-dimensional manner from the growth interface to the low-temperature portion where the cooling progressed. This result revealed that Vs are uniformly introduced in a grown crystal regardless of the pulling rate as long as the growth continues, and the Vs agglomerate as a void and remain in the crystal, unless recombined with Is. On the other hand, Is are generated only in a region where the temperature gradient is large by low-rate growth. In particular, the generation starts near the peripheral portion in the vicinity of the solid–liquid interface. First, the generated Is are recombined with Vs introduced into the growth interface, so that a recombination region is always formed which is regarded as substantially defect free. Excessively generated Is after the recombination agglomerate and form a dislocation loop region. Unlike conventional Voronkov's diffusion model, Is hardly diffuse over a long distance. Is are generated by re-heating after growth.[In a steady state, the crystal growth rate is synonymous with the pulling rate. Meanwhile, when an atypical operation is performed, the pulling rate is specifically used.]This review on point defects formation intends to contribute further silicon crystals development, because electronic devices are aimed to have finer structures, and there is a demand for more perfect crystals with controlled point defects. 相似文献