基于第一性原理计算的共掺型p型ZnO光电学特性对比

Comparative Study on the Photoelectric Properties of Co-Doped p-type ZnO Based on First Principles Calculation

基于DFT的第一性原理研究了本征ZnO和Ag单掺、Ag-F(或N)共掺ZnO体系的晶格结构、电子结构和光学性质。结果表明:各掺杂体系与本征ZnO相比晶格常数a、c和晶胞体积基本都有所增大;虽然N3-离子半径高于F-,但Zn_(15)AgO_(15)N晶胞体积低于Zn_(15)AgO_(15)F,是由于Zn_(15)AgO_(15)N体系的Ag-O和N-Zn键长均低于Zn_(15)AgO_(15)F体系的Ag-O和F-Zn键长,且Zn_(15)AgO_(15)N体系结构更稳定;Zn_(15)AgO_(15)N体系中杂质能级有所降低,所需电离能降低,杂质更易电离,Ag4d、N2d和O2p态电子在VBM处形成杂化;Zn_(15)AgO_(15)N在紫外光区和可见光区的吸收率和反射率上有较大的增强。Zn_(15)AgO_(15)F体系由于施主-受主的补偿效应,导致了总体结构的不导电,可以看出Zn_(15)AgO_(15)F共掺不适合用于ZnO的p型转化,而Zn_(15)AgO_(15)N双受主型共掺实现了浅施主能级的p型转化,且具有较好的光电学特性。因此Ag-N共掺形式实现的p型ZnO在紫外短波长光电子器件上的应用具有一定的潜力。

The first principles based on density functional theory(DFT)were introduced to study the lattice structure, electronic structure and optical properties of pure ZnO and Ag mono-doped and Ag-F(or N) co-doped ZnO systems.The results show that compared with pure ZnO,the lattice constants a,c and supercell volume of each doped system are basically increased.Although the radius of N3-ions is higher than that of F-,the cell volume of Zn_(15)AgO_(15)N is lower than that of Zn_(15)AgO_(15)F,which is because the Ag-O and N-Zn bond lengths of Zn_(15)AgO_(15)N system are lower than the Ag-O and F-Zn bond lengths of Zn_(15)AgO_(15)F system, and the structure of Zn_(15)AgO_(15)N is more stable.In Zn_(15)AgO_(15)N system, the impurity level is reduced, which leads to a lower ionization energy, the impurity is easier to ionize.Meanwhile, the electrons of Ag4d, N2d and O2p states are hybridized at VBM.The absorption coefficient and reflectivity of Zn_(15)AgO_(15)N in ultraviolet and visible regions are enhanced greatly.Due to the compensation effect of donor-acceptor, the overall structure of Zn_(15)AgO_(15)F system is not conductive, it can be seen that the Ag-F co-doping is not suitable for p-type transformation of ZnO.However, Ag-N co-doping successfully obtained p-type ZnO with shallow donor level and good photoelectric properties.This may provide a certain basis for the application of Ag-N codoped ZnO in ultraviolet short wavelength photoelectronic devices.