Design of shallow acceptors in ZnO through compensated donor-acceptor complexes: A density functional calculation

Abstract

The intrinsic large electronegativity of $\text{O}\text{ }2p$ character of the valence-band maximum (VBM) of ZnO renders it extremely difficult to be doped $p$ type. We show from density functional calculation that such VBM characteristic can be altered by compensated donor-acceptor pairs, thus improve the $p$-type dopability. By incorporating $(\text{Ti}+\text{C})$ or $(\text{Zr}+\text{C})$ into ZnO simultaneously, a fully occupied impurity band that has the $\text{C}\text{ }2p$ character is created above the VBM of host ZnO. Subsequent doping by N in $\text{ZnO}:(\text{Ti}+\text{C})$ and $\text{ZnO}:(\text{Zr}+\text{C})$ lead to the acceptor ionization energies of 0.18 and 0.13 eV, respectively, which is about 200 meV lower than it is in pure ZnO.