Investigations of centers formed in UV-light-induced absorption for LiNbO3highly doped with Mg and Hf

UV-light-induced absorption in LiNbO(3) highly doped with Mg and Hf was investigated. Distinct decay behavior was attributed to the different centers formed under UV illumination, i.e., the shallow and intermediate deep centers for trapping holes. O- formed near doped cation at the niobium site was suggested to be the origin of the shallow center, whereas that formed near cation vacancy was suggested to be the origin of the intermediate deep center. The influence of the sample status (oxidized or reduced) on the UV-light-induced absorption was demonstrated to support our suggestion. Two different dark decay processes were associated with relaxations of holes from the shallow centers to two unequivalent Nb(Nb) adjacent to the doped cations at niobium sites.