Charge states of a hydrogen defect with a local vibrational mode at 3326 cm-1 in ZnO

An IR absorption study is presented of a hydrogen defect in ZnO that gives rise to a local vibrational mode at 3326 cm(-1) [M. D. McCluskey et al., Appl. Phys. Lett. 81, 3807 (2002)]. It is shown that a subband gap illumination results in the appearance of a new IR absorption line at 3358 cm(-1) at the expense of the main signal at 3326 cm(-1). Based on the anticorrelation between the two lines as well as on the results of isotope substitution experiments it is concluded that both signals are due to stretch modes of an O-H bond of the same defect in different charge states. The energy of the subband gap light strongly suggest that this defect has a deep rather than shallow level in the band gap of ZnO. Additionally, the results on thermal stability, uniaxial stress response, and temperature dependence of the transition rates between the two charge states of this defect are presented.