The Study Of ZnSe/Si Heterosturcture Nanowires

Semiconductor heterostructure nanowires have been received considerable attentions because theses nanowires have special morphologies and properties which the bulk don't own. This paper, which has been investigated by means of first-principle calculations within density functional theory as implemented by the CASTEP, mainly studies the structural stabilities and electronic properties of ZnSe/Si heterostructure nanowires, in order to provide theoretical bases for the future fabrications of nano-size devices.First, the structural stabilities of bare and hydrogen-passivated ZnSe heterostructure nanowires oriented along the (110) direction are investigated. It has been found that all the atomic positions are fully optimized. Upon relaxation, the structures of the nanowires are reconstructured. Based on doping Si in ZnSe/Si nanowires have great lattice distortion,with atom relaxation range greater at heterojunction's surface compared with normal level, while smaller at heterojunction's center. It has been well known, that the lattice parameter of ZnSe bulk is larger nearly 4% than Si, so the lattice parameters of synthetical nanowires with composition are deviated from Veagrd's law and exhibit nonlinear dependence. However, the decrease trend of lattice parameters remain unchanged with the increase of concentration of Si dopant.Secondly, cohesive energy is another important parameter in order to discuss the structural relative stability of nanowires. It is found that hydrogen-passivated nanowires are generally more favorable with respect to add the number of Si atoms, and it can be easily fabricated.Moreover, we investigate the effect of dangling bonds and find bare ZnSe/Si heterostructure nanowires are generally metallic. The dangling bonds saturated by hydrogen atoms can help to eliminate dangling bond's effect on nanowires electronic properties and attribute semiconductive characters to ZnSe/Si nanowires by our analysis. Furthermore, a growing research interest has been devoted to doping different concentration of Si atoms in the hydrogen-passivated nanowires. We find that the band gap of pure Si nanowire is direct bandgap and it is greater than that of bulk Si. It is worthwhile to point out that passivated ZnSe/Si nanowires can be modified as n-type or p-type through doping different concentration of Si atoms. At low Si concentration, the Fermi level occurs near the conduction band edge, the energy gaps of n-type semiconducting structures are highlighted. Conversely, nanowires semiconductor can be modified as p-type through doping relative high concentration of Si atoms. These results provide important informations for their potential applications in optical and electronic areas.In the last section, we introduce another research result about the effect of Ga/N co-doping on Electronic Structure of InSb. The electronic structure and electronic property of zinc blende InSb co-doped with Ga and N is investigated. It is found that there is a small effect on the band gap of InSb co-doped with Ga or N. With the increase of N concentration, the semiconductor of InSbN can be also modified as zero gap. However, the band gap is changed obviously with the concentration changing of the co-doped Ga/N.