Energy states of Ge-doped SiO₂ glass estimated through absorption and photoluminescence

The energy states of oxygen-deficient type defects in the vacuum ultraviolet region are discussed based on the experimental results of vacuum ultraviolet absorption, temperature dependence of the photoluminescence (PL) intensities at 4.3 and 3.1 eV, and lifetimes of the PLs. It was found that the oxygen-deficient type glass has a large absorption tail above 6 eV in addition to an absorption band around 5 eV and that the 3.1 eV PL intensity scarcely depends on temperature when excited above 6 eV. It was also found that the lifetime of the 4.3 eV PL is 9 ns and that of the 3.1 eV PL is 113 μs irrespective of the excitation photon energy. The obtained results are explainable by assuming that electrons excited into the conduction band by photons above 6 eV contribute to the PLs.