Infrared spectroscopy of hydrogen in annealed zinc oxide

Zinc oxide (ZnO) has shown great promise as a wide band gap semiconductor with optical, electronic, and mechanical applications. First-principles investigations by C. G. Van de Walle (Phys. Rev. Lett. 85 (2000) 1012) suggest that hydrogen may act as a shallow donor in ZnO. These same predictions also apply to deuterium (D). Using IR spectroscopy we have observed O-H and O-D stretch modes at 3326.3 and 2470.3 cm-1, respectively, in the same sample at a temperature of 14 K. These frequencies are in good agreement with the theoretical predictions for hydrogen and deuterium in an antibonding configuration. We have also performed preliminary polarization measurements at room temperature showing that the dipole of the O-H complex does not lie parallel to the c-axis of wurtzite ZnO