硅基半导体光电子材料的第一性原理设计

具有特定功能的半导体材料的计算设计，是计算材料科学的一个重要研究领域．由于半导体的诸多性质取决于价带顶和导带底的电子态及其中的载流子分布，因此带隙的大小和能带极值的对称性便成为半导体材料设计最受关注的问题．为了进一步解决硅基光电子集成（OEIC）技术发展的瓶颈．设计具有直接带隙特性的硅基新材料并使其成为有效的光发射体，是一项富有挑战性的工作．本文在分析大量半导体能带结构的基础上，给出类sp系列半导体由间接带隙过渡到直接带隙的主要物理机制，并以对称性概念、芯态效应和电负性差效应为基础，提出一种新的直接带隙半导体材料设计方案．根据这个方案所表达的设计思想，我们对当前十分受关注的硅基光发射材料进行了计算设计．结果发现，用VI族元素在硅生长时进行周期性插层的、具有正交和四角点群对称性的人工微结构材料VIA／Sim／VIB／Sim／VIA具有直接带隙特性．其中当m=5或奇数时，材料有四角结构对称性，而m=6或偶数时是正交结构对称性．VI“。。是在〈001〉生长方向生长的单层VI族元素．这类材料的优点在于可自然地与硅实现晶格匹配，与微电子技术相兼容，并可较容易的用现行的MBE、MOCVD或UHV-CVD生长方法实现．预期这类新材料及其相应器件的研制开发．将大大开拓全硅OEIC和硅光子集成（PIC）技术的进一步发展．

An ab initio Computational Design of Si-based Optoelectronic Materials

A computational design of the semiconductor materials with specific functional has been became an important research field in computational materials science.Owing to the properties of the semiconductor are depended on the electronic states and the current carrier distribution at valence band top and conduction band bottom,therefore the band-gap values and the symmetry of the band extremes are the most attention problems in materials design.In order to solve the bottleneck in the technical development of all-silicon optoelectronic integration circuit,to design a Si-based new materials with direct band-gap and make it,as an effective light emitter is a challenge work.On the basis of the band-gap type analysis to many semiconductors,the main mechanisms of the band-gap type transition from indirect to direct gap are given in this paper.A new scheme for obtaining direct-gap semiconductors is suggested based on the symmetry concept,core-states effect and electronegativity differences effect of the component atoms.These idea leads us to design the Si-based materials and the results shown that the new micro structure materials with formula VI_A/Si_m/VI_B/Si_m/VI_A are the direct gap semiconductors,in which the crystal symmetry is tetragonal(for m=5 or odd) and orthorhombic(for m=6,even).The VI_(A(B)) is a monolayer VI group elements in the grown direction <001>.The advantage of these materials is that the lattice parameter can be spontaneous matching with Si(001) and the fabrication technology will be compatible with silicon microelectronic technology.The materials may be easy to realize by a convenient scheme such as MBE,MOCVD and UHV-CVD methods.It is expect that the development of these new materials and related devices will exploit a more progress of the all-silicon OEIC and silicon photonic integration circuit(PIC).