| Zn O is a direct band-gap semiconductor(Eg=3.3e V at RT) with a high exciton binding energy of about 60 me V. The feasibility of using excitionic lasers of Zn O at RT has been demonstrated. Zn O is a very promising material for blue and ultraviolet light-emitting devices, gas sensors, surface acoustic wave devices, piezoelectric devices, high temperature microelectronic devices and photoelectron devices, et al.In this article, electronic structure, doping and optical properties are investigated from first-principles of plane wave ultra-soft pseudo-potential method based on density function theory. The main contents are presented as follows:Firstly, first-principles study of the electronic structure and optical properties of different acceptor complex with Li, N codoped Zn O are performed. We used the method of the plane-wave pseudo-potential to calculate the variationsof the electronic structure and optical properties of Zn O system before and after doping and analyzed the impact of the doping on the crystal structure and properties of Zn O.Theoretically, the correlation between the electronic structure and optical properties of Zn O materials with dopants are given.Then the lattice constant, crystal structure, band structure, electron density of states, dielectric function and absorption coefficient of intrinsic and doped Zn O are calculated. The results show that, with the incorporation of Li, N,the lattice constants, the bond length and volume increase. The formation energy of the system is negative and as a result, the stability of structures enhances. As Li, N are doped, the Fermi energy level moves into the valence band and the hole carriers increase, which indicates that the crystal becomes P type. However, in the case of four acceptors doping, the crystal become N typewhile Li-N complex are adjacent andbothof them parallelto the Caxis. This phenomenonis also observedin the case of the high concentration of Li, N co-doped Zn O, where the system formation energy of k(Here k is the structure which means Li-2N complex and adjacent Li-N unparallel to caxis doped Zn O) is alsovery low. The interactionbetween impurity atoms could decrease the formation energy of the system and it leads to donor compensation.The formation energy of structure l(Here l stands for the structure which contains Li-2N complex and nonadjacent Li–N parallel to C doped Zn O) and m(Here m is the structure which contains two nonadjacent Li-2N complex)are positive that indicate high concentration of Li, N codoped Zn O is not allowed。Secondly, first principles study on electrical structure of M2-2N co-doped Zn O is performed.The electronic structure and optical properties of the intrinsic Zn O and Li2-2N co-doped Zn O are calculated. We found that the formation energy of this special structure is negative and the crystal becomes N type. Then,we build the M2-2N structure,where M means the atom which substitute Zn like Na, K, Ca, Cu, Mg, Al etc,N is nitrogen.Through comparative analysis, we found that the crystal becomes N type when Na, K etc is codoped with nitrogen.While Ag, Ba, Mg is codoped with N the crystal becomes Ptype.The difference incharge density show that when Li, Na, K is codoped with N element, covalent bonds will be formed between different N atoms and the complex will becomesdonor compensation.We hope our results offer meaningful data for the design and application of optoelectronic materials of Zn O. Meanwhile, the calculated results are also applied in more precise monitoring and controlling during the growth of Zn O semiconductor materials. |
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