磷属化物和硫属化物半导体合金的电子结构和玻璃化转变。第II部分：本征电子中间带隙态
Electronic structure and the glass transition in pnictide and chalcogenide semiconductor alloys. Part II: The intrinsic electronic midgap states
摘要：
我们提出了一个结构模型，在一个统一的方式对待淬火熔体中的磷族元素化物和硫族元素化物半导体的原子运动和电子激发。在第一部分（提交给J. Chem. Phys.）中，我们认为这些淬灭的熔体代表了高度稳定的非周期性$ppσ$ -网络，同时，结构退化。这些网络的特点是协调范围不断扩大。在这里，我们提出了一个系统的方法来分类这些类型的协调在一个简单的立方晶格上定义的父结构中的离散的协调缺陷。我们确定了最低能量的配位缺陷与半导体玻璃中的本征中间带隙电子态，这是以前认为在这些材料中造成许多独特的光电异常。此外，这些配位缺陷是移动的，并对应于过渡态配置在玻璃化转变以上的活化运输。配位缺陷的存在可以解释硫族化合物中动力学和热力学脆性之间令人困惑的差异。最后，所提出的模型恢复作为限制性的情况下，几种流行的类型的键合模式提出了较早的，包括：价交替对，超价配置，并在异极化合物的同极键。
英文摘要：
We propose a structural model that treats in a unified fashion both the atomic motions and electronic excitations in quenched melts of pnictide and chalcogenide semiconductors. In Part I (submitted to J. Chem. Phys.), we argued these quenched melts represent aperiodic $ppσ$-networks that are highly stable and, at the same time, structurally degenerate. These networks are characterized by a continuous range of coordination. Here we present a systematic way to classify these types of coordination in terms of discrete coordination defects in a parent structure defined on a simple cubic lattice. We identify the lowest energy coordination defects with the intrinsic midgap electronic states in semiconductor glasses, which were argued earlier to cause many of the unique optoelectronic anomalies in these materials. In addition, these coordination defects are mobile and correspond to the transition state configurations during the activated transport above the glass transition. The presence of the coordination defects may account for the puzzling discrepancy between the kinetic and thermodynamic fragility in chalcogenides. Finally, the proposed model recovers as limiting cases several popular types of bonding patterns proposed earlier, including: valence-alternation pairs, hypervalent configurations, and homopolar bonds in heteropolar compounds.
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