Luminescence of Ga‐Doped α‐Al 2 O 3 Crystals

The introduction of Ga 3+ ions into α‐Al 2 O 3 crystals results in a new complex luminescence band at about 5 eV. The main optical excitation maximum is observed at 8.5 eV indicating the bound exciton nature of the excited state. In the cathodoluminescence spectra at 80 K three sub‐bands can be detected with maxima at 4.61, 5.15, and 5.58 eV. The luminescence decay in all the three bands has two exponential components — a short one with τ = (15 ± 1) ns and a long one with τ about 1 ms. The Ga‐related luminescence can be observed under the excitation of X‐rays up to 600 K; a drop in intensity takes place at about 210 K corresponding to the Ga‐related TSL peak. The activation energy of the release of electrons at this peak as determined by the fractional‐glow method is (0.70 ± 0.02) eV and the frequency factor 10 14 s −1 .