First-principles study of the electronic structure and defect properties of transparent oxide semiconductors and diluted magnetic semiconductor nanowires

Abstract

Using first-principles calculations, we study three interesting subjects, (1) the origin of $p$-type conductivity in phosphorus-doped ZnO, (2) the structural and electronic properties of crystalline $InGaO_3(ZnO)_m$, and (3) the magnetic properties of Mn-doped InN nanowires. First, we investigate the defect properties of various phosphorus(P)-related defects and $p$-type doping efficiency in P-doped ZnO, where $p$ -type conductivity is an important issue for optoelectronic applications. We consider substitutional defects such as a substitutional P at an $O site(P_O)$ and at a Zn site $(P_{Zn})$, and defect complexes such as a $P_2$ molecule at an O site $((P_2)_O)$ and $P_{Zn}-2V_{Zn}$, which consists of a substitutional P at a Zn site and two Zn vacancies. A substitutional P at an O site behaves as a single acceptor with the high transition level of about 0.62 eV and is the most stable acceptor under Zn-rich growth conditions. However, because of the high transition level and the compensation effect by the shallow triple donor a $P_{Zn}$, $P_O$ is difficult to lead to $p$-type conductivity. A $P_{Zn}-2V_{Zn}$ complex acts as an acceptor and is easily formed under O-rich growth conditions. Moreover, under O-rich growth conditions, the compensation by a $P_{Zn}$ is weakened and then $P_{Zn}-2V_{Zn}$ defect complexes could cause $p$ -type conductivity. In addition, we consider a $P_O-V_{Zn}$ defect complex, which can be generated by the diffusion of $V_{Zn}$ and the binding of $P_O$ with $V_{Zn}$ under Zn-rich conditions. A $P_O-V_{Zn}$ complex is a double acceptor and can be the source of $p$ -type conductivity together with $P_{Zn}-2V_{Zn}$ complex and $V_{Zn}$ under non-equilibrium growth conditions such as thermal annealing. We discuss the acceptor and donor levels in the LDA+U calculations, which improve the band structure of ZnO. Next, we investigate the atomic and electronic properties of crystalline $InGaO_3(ZnO)_m$, which is composed of the alt...