Comparison of electronic structures of doped ZnO by various impurity elements calculated by a first-principle pseudopotential method

Abstract

Electronic band calculations of ZnO doped with Li, Al, Ga, In, Si, Ge, Y, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu have been done within a framework of local density approximation, and partial densities of states (PDOSs) of dopants have been evaluated. PDOS of Al(Ga, In) of ZnO : Al(Ga, In) has delocalized nature, which is considered to be responsible for good conductivity of Al-doped ZnO. PDOS values of Cu and Li of ZnO : Cu and ZnO : Li are quite small at their Fermi levels (E_Fs), and this may be one of the possible reasons for their insulating nature as well as the compensation effects. PDOS values of Si and Ge of ZnO : Si and ZnO : Ge at their E_Fs are relatively large but are less delocalized compared to that of ZnO : Al(Ga, In). As for ZnO : Y, ZnO : Ti, and ZnO : V, PDOS values of Y(Ti, V) are small at their E_Fs. ZnO : Cr and ZnO : Mn have isolated impurity levels between the energy gap of ZnO and their E_Fs are located on these levels, seemingly resulting in poor conductivities. E_Fs of ZnO : Fe(Co, Ni) are located near the top of the valence band, and PDOS values of Fe(Co, Ni) at their E_Fs are relatively large. Their semiconducting nature might be caused by strong correlation between electrons which is beyond the description of a band calculation.