Thermodynamic Database for Alloy Semiconductor Systems.

III-V型化合物半导体（III=AI, Ga, In: V=P, As, Sb）具有Si半导体所不能获得的各种优异性能。此外，这些化合物的混合物被称为III-V型晶体合金半导体，这使得通过其组成任意控制其带隙能和晶格常数等物理性质成为可能。因此，III-V晶合金半导体在光电子和高速器件中具有重要意义。为了实现理想的性能，即在接近相平衡的条件下通过液相外延（LPE）方法制备具有适当成分的晶体合金，相图是控制其显微组织和成分的必要手段。然而，据报道，衬底上的薄外延层表现出与块体材料完全不同的相平衡，如平衡成分的偏差，意想不到的pha的形成等。本研究基于热力学数据和实验结果，对III-V晶合金半导体的相平衡进行了热力学分析。然后，建立了计算体层和薄层材料相平衡的热力学数据库。液相和化合物的吉布斯能分别用亚规则溶液近似和双亚晶格模型来描述。在计算衬底上生长的薄外延层的稳定性时，考虑了应变能。对11种三元体系的热力学参数进行了评价，建立了考虑外延层与衬底之间应变能和不考虑外延层与衬底之间应变能的III-V合金半导体热力学数据库。当GaAs-GaSb晶体合金在lnP衬底（100）平面外延生长时，可以看到晶体层与衬底之间外延所引起的应变能的影响。根据计算结果，当其厚度为0时，其组成为5 lmol% GaAs时，出现了意想不到的均匀相，对应于晶格匹配成分。这与Quillec等人的LPE实验结果吻合较好。对薄层与衬底之间的各种组合的计算结果表明，外延层的相稳定性取决于衬底的晶格常数和晶体取向以及外延层的厚度。少

III-V compound semiconductors (III=AI, Ga, In : V=P, As, Sb) have various outstanding properties which can not be obtained by Si semiconductor. Furthermore, mixture of these compounds which is called as III-V crystal alloy semiconductor gives possibilities to control its physical properties arbitrarily such as the band gap energy and the lattice constant by its composition. Therefore, III-V crystal alloy semiconductors are of great significance for opto-electronics and high-speed devices. In order to realize the desirable properties, i.e., to create the crystal alloy with appropriate composition by Liquid Phase Epitaxy (LPE) method under the condition of near phase equilibria, phase diagrams are indispensable for controlling their microstructures and compositions. However, it was reported that a thin epitaxial layer on a substrate exhibited completely different phase equilibria from those of bulk materials, for instance, deviation of equilibrium composition, formation of unexpected pha … More ses and so on. In this research, thermodynamic analysis on the phase equilibria of III-V crystal alloy semiconductor was carried out based on the thermodynamic data and experimental results. Then, thermodynamic database has been established for calculating the phase equilibria of both bulk and thin layer materials.Gibbs energies of the liquid phase and the compound are described by the sub-regular solution approximation and the two-sublattice model respectively. The strain energy was taken into account for calculating the stability of a thin epitaxial layer grown on a substrate.Thermodynamic parameters of eleven ternary systems have been evaluated and thermodynamic database for III-V alloy semiconductors has been constructed with or without taking account of a strain energy between a epitaxial layer and a substrate. The effect of the strain energy which is caused from the epitaxy between a crystal layer and a substrate can be seen, for instance, when a GaAs-GaSb crystal alloy is grown epitaxially on the (100) plane of lnP substrate. According to the result of calculations, unexpected homogeneous phase appears when its thickness is him and its composition is 5 lmol% GaAs which corresponds to the lattice matching composition. This is in good agreement with the experimental result of LPE by Quillec et al. The results of calculations for various combinations between thin layers and substrates show that phase stability of an epitaxial layer depends on the lattice constant and the crystal orientation of the substrate and on the thickness of the epitaxial layer. Less