Photoluminescence spectra of perovskite oxide semiconductors

We report photoluminescence (PL) spectra of typical wide-gap perovskite semiconductors, SrTiO3, KTaO3, BaTiO3, LiNbO3, and LiTaO3. In SrTiO3, KTaO3, and BaTiO3, undoped crystals show no PL at room temperature, while broad PL bands appear by Ar+ irradiation. The room temperature PL properties of SrTiO3, KTaO3, and BaTiO3 are very similar to each other, but are different from those of LiNbO3 and LiTaO3. At low temperatures, only Ar+-irradiated SrTiO3 crystals show sharp band-edge PL, corresponding to the band-to-band radiative recombination of free electrons and holes. Unique PL behaviors in SrTiO3 are discussed, compared to other perovskite oxides.