Band-to-band photoluminescence in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>SrTiO</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

We report the observation of band-edge photoluminescence (PL) in highly photoexcited ${\text{SrTiO}}_{3}$ and electron-doped ${\text{SrTiO}}_{3}$ at low temperatures. Two band-edge PL peaks coincide with the low- and high-temperature onsets of optical absorption. This clearly shows that band-edge PL peaks correspond to indirect band-to-band radiative recombination involving phonon emission and absorption processes and allows a determination of the band gap. The PL peaks redshift with increasing carrier density, indicating band-gap shrinkage. The temperature dependence of the band-edge PL and optical absorption spectra are also discussed in conjunction with phonon-assisted optical transitions.

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