Physics and control of valence states in ZnO by codoping method

We investigate unipolarity in ZnO based on ab initio electronic band structure calculations. We find that p-type doping using Li, N or As species causes an increase in Madelung energy, n-type doping using B, Al, Ga, In or F species gives rise to a decrease in Madelung energy. In order to solve the unipolarity, to fabricate p-type ZnO, we propose a codoping method using acceptors and reactive donors simultaneously. A codopant pair including Ga-reactive donors and N-acceptors is eminently suitable for use in the codoping. For Li-acceptors. F species is a good candidate for reactive donors. For As-accepters, Ga species is a preferable codopant. (C) 2001 Elsevier Science B.V. All rights reserved.