p-type doping and codoping of ZnO based on nitrogen is ineffective: An <i>ab initio</i> clue

Abstract

Whereas nitrogen is regarded as the best candidate to induce p-type doping in ZnO, the practical results are mainly negative either for monodoping or codoping. We perform first-principles calculations to investigate the p-type nature of boron and nitrogen codoped ZnO. The p-type character can be obtained with the proper BN3 substitutional clusters. We propose a mechanism that explains the difficulties to synthesize p-type ZnO samples: the formation of N2 molecules substituting oxygen, which are donors, energetically prevails over any codoping cluster. This mechanism is very general and explains the experimental instability of N-based doping and codoping versus time and temperature.