Interstitial hydrogen in ZnO and BeZnO

First principles calculations show that for both ZnO and BeZnO phases, H prefers the positive charge state and would bring about n-type conductivity as a donor, while H0 and H− are energetically unfavorable with positive heat of formation. Calculation also reveals that H+ would probably occupy both bond-centered and anti-bonding sites due to a big migration barrier of site diffusion, which could therefore give a reasonable explanation to the experimental controversy regarding the location of H+ in the literature. Interestingly, the addition of Be could increase the stability and migration barrier of H+ in ZnO, and such an effect would be attributed to a stronger chemical bonding around the H atom formed in BeZnO. In addition, it is found that all the H+, H0, and H− states would bring about a decrease of the band gap of ZnO and BeZnO due to the splitting of degenerate bands and leftward moving of energy bands.