Luminescence of Ga-Doped alpha -Al sub(2)O sub(3) Crystals

The introduction of Ga super(3+) ions into alpha -Al sub(2)O sub(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 tau = (15 plus or minus 1) ns and a long one with tau 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 plus or minus 0.02) eV and the frequency factor 10 super(14) s super(-1).