Effects of intentionally introduced hydrogen on the electrical properties of ZnO layers grown by metalorganic chemical vapor deposition

Unintentionally doped ZnO layers grown epitaxially on a sapphire substrate have been exposed either to a hydrogen or deuterium plasma. Secondary ion mass spectroscopy measurements performed subsequently showed a rapid diffusion of hydrogen in these layers. Furthermore, the presence of hydrogen in the ZnO samples is found to be responsible for nearly a factor of 3 increase in the free electron concentration. This effect is attributed to the hydrogen passivation of compensating acceptor impurities present in the as-grown ZnO layers.