Luminescence of gallium doped MgO and CaO single crystals

Cathodoluminescence (CL) of MgO-Ga and CaO-Ga was studied. For MgO-Ga the photoluminescence (PL) excitation spectra were measured as well as the CL kinetic characteristics. The CL was excited with an electron gun at electron energies 2-10 keV. An intense complex band is observed at 3.5 eV in the PL and CL spectra of MgO-Ga and CaO-Ga both at 80 and 300 K. The main photoexcitation band of this luminescence in MgO-Ga is at 7.15 eV. The decay of CL obeys the hyperbolic law but from the first stage of decay a time constant of 2-4 sec can be evaluated. The luminescence at 3.5 eV is suggested to be due to transitions in Ga+ centers. At 80 K and Ga concentration about 0.01 mol. and more MgO-Ga presents the second CL band at 4.55 eV. The CL decay in 4.55 eV band is approximated by the sum of two exponents with characteristic time (4.5+-0.1)x10-6s and (6.2+-0.1)x10-5 s