Effect of compressive stress on doping efficiency of nitrogen in ZnO films

Nitrogen (N)-doped ZnO films (ZnO:N) grown on the a-/c-plane sapphire substrates (a-/c-Al2O3) by plasma-assisted molecular beam epitaxy were investigated. It was found that the content of N in the ZnO films grown on c-Al2O3 is higher than that of the films grown on a-Al2O3. The ZnO:N films grown on c-Al2O3 have lower carrier concentration and larger intensity ratio of the DAP/D°X emission compared with those of the ZnO:N films grown on a-Al2O3 under the same growth conditions, which indicates higher incorporation efficiency of N in the ZnO films grown on c-Al2O3.