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).