Most of the ZnO growth techniques result in n-type conductivity of the crystal, which hinders the progress of ZnO applications for electronic devices. Hydrogen incorporated during the process of crystal growth was now considered as a likely source of the n-type conductivity of ZnO. Infra-red absorption spectroscopy provided detailed insights into the physical properties of the light impurities in semiconductor matrix and was therefore an excellent tool for exploring the structure of H-related defects in ZnO. A number of H-related defects observed in hydrothermal grown ZnO and ZnO grown from the vapor phase were studied by Fourier transform infra-red absorption spectroscopy. Three IR absorption lines at 3611.3, 3349.6 and 3312.2/cm at 10K were observed after hydrogenation of the vapor phase grown ZnO. The line at 3611.3/cm was tentatively attributed to a bond-centered H, whereas the other 2 were identified as being a Zn vacancy decorated with two H atoms. A Ni–H complex with a H atom primarily bound to O was suggested to be responsible for the 3577.3/cm line observed at 10K in as-grown hydrothermal ZnO.

Infrared Absorption Spectroscopy of Hydrogen-Related Defects in ZnO. Lavrov, E.V.: Physica B, 2003, 340-342, 195-200