Temperature Dependence of Photoluminescence Spectra of Nondoped and Electron-Doped SrTiO₃: Crossover from Auger Recombination to Single-Carrier Trapping

We report unusual photoluminescence (PL) behaviors in highly photoexcited SrTiO₃ crystals at low temperatures. The PL spectrum and dynamics show abrupt changes below 150 K in both nondoped and electron-doped SrTiO₃ samples. We clarified that the PL dynamics in both nondoped and electron-doped SrTiO₃ is well described by the same simple model involving single-carrier trapping, radiative bimolecular recombination, and nonradiative Auger recombination. The unusual temperature dependence of PL dynamics is caused by the crossover from Auger recombination at high temperatures to single-carrier trapping at low temperatures. We discuss the temperature-dependent PL dynamics in conjunction with the high carrier mobility of SrTiO₃ at low temperatures.