Hydrogen passivation effect in nitrogen-doped ZnO thin films

Abstract

The role of hydrogen in nitrogen-doped ZnO thin films was studied by Fourier transform infrared (FTIR) absorption and modeled by first-principles calculations to understand the difficulty of dopingZnO p -type with nitrogen. Nitrogen-doped ZnOfilms were fabricated by low-pressure metal-organic chemical vapor deposition(MOCVD). High levels of nitrogen incorporation were observed, but the acceptor concentrations remained low. Theoretical analysis suggests there is a high probability that N O − and H + charged defects combine to form the neutral defect complexes, thereby compensating the nitrogen-related acceptors. Calculated values of the vibrational frequencies of the related infrared modes agree well with the measured spectra. Thus, we believe the difficulty of achieving p -type doping in MOCVD-grown ZnOfilms is due, at least partially, to inadvertent passivation by hydrogen.