Structural and electronic properties of cubic boron nitride doped with zinc

Abstract

Structural and electronic properties of Zn-doped cubic boron nitride (cBN) were investigated via first principle calculation based on density functional theory. Our simulation suggests that Zn can substitute for both B (ZnB) and N (ZnN) atom; ZnB is energetically favorable, and ZnN can only be prepared under B-rich conditions. ZnB induced a shallow acceptor level; however, the large difference in electronegativity between Zn and N makes the acceptor level strongly localized, which reduces effective carrier density. In the case of ZnN, both deep acceptor levels within band gap and shallow acceptor levels at the top of valence band were induced, which produced more free carriers than ZnB. The calculated results account for experimental results of enhanced electric conductivity of Zn-doped cBN films prepared under B-rich conditions.