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半绝缘Ⅲ-Ⅴ族材料作为衬底广泛用于非常高速的微波或亚微波集成电路,并且使用者总是不断地要求改进其质量,特别是从各类缺陷的观点,如位错和点缺陷。这些缺陷被认为在复合机理中起重要作用。将讨论一个新的生长体单晶的方法,它能减少或者至少能对两种类型的缺陷有较好的控制。首先回顾一下与常规的布里支曼法和LEC法生长的大小晶锭中各类缺陷存在有关的技术发展状况。然后表明,一个非掺杂晶体,当它的直径不超过15mm时,可得到无位错。通过对较小锭的研究,结合热梯度及有关应力计算,我们可做出这样的结论:大于它,位错产生的临界切应力(CRSS)对于各个晶体是不一样的。临界切应力明显地依赖于材料的初始状态,特别是晶体的化学配比,本身的点缺陷行为及在刚好低于熔点温度时它们与杂质间的相互作用。通过采用一种新的叫做克氏液封法来减少生长期间的热应力或者通过施主或等电子元素掺杂来增加晶体的CRSS,都可以得到位错少的晶体。在这方面最先进的结果是可得到直径为25mm的无位错GaAs。在上述两种情况下,点缺陷的变化都随着发生,特别是深能级施主EL2在GaAs晶体中的浓度。给出存在于这些晶体中杂质浓度的看法,表明这些研究将有助于得到具有低位错密度和高纯度的半绝缘材料。
Semi-insulating III-V materials are widely used as substrates for very high speed microwave or sub-microwave integrated circuits, and users are constantly required to improve their quality, particularly from the viewpoint of various types of defects such as dislocations and point defects . These defects are believed to play an important role in the complex mechanism. A new method of growing single crystals will be discussed, which reduces or at least provides better control over both types of defects. First, review the state of the art related to the existence of various types of defects in ingots of the same size as those grown by the conventional Buritian and LEC methods. Then it is shown that an undoped crystal can be dislocated when its diameter does not exceed 15 mm. By studying the smaller ingots, combined with the thermal gradient and related stress calculations, we can conclude that above this, the critical shear stress (CRSS) produced by dislocations is not the same for each crystal. The critical shear stresses depend significantly on the initial state of the material, in particular the stoichiometry of the crystals, their point defect behavior and their interaction with the impurities just below the melting temperature. Dislocation-less crystals can be obtained by using a new CRS method called Kirschner’s Sealer to reduce the thermal stress during growth or by increasing the CRSS of the crystal by donor or alloying with other alloying elements. The most advanced result in this respect is that dislocated GaAs with a diameter of 25 mm can be obtained. In both cases, changes in point defects occur with the concentration of deep-level donor EL2 in the GaAs crystal, as it occurs. Given the perception of the presence of impurities in these crystals, these studies will help to obtain semi-insulating materials with low dislocation density and high purity.