Luminescence and Conductivity of β-Ga2O3 and β-Ga2O3:Mg Single Crystals

The temperature-dependencies of the X-ray excited luminescence spectra were measured from unintentionally doped, annealed in oxygen and Mg-doped beta-Ga2O3 crystals prepared by the floating zone growth method. The crystals exhibited ultraviolet, blue and green luminescence bands. It was established that the luminescence intensity is strongly dependent on resistivity of the crystal. For the as-grown sample with a high electron concentration, the main luminescence band at 300 K was blue. The blue luminescence band was observed over a wide range of temperatures, and the thermal quenching of luminescence was observed only at T > 400 K. The blue luminescence band was suppressed in high-resistance crystals, in particular in oxygen annealed and heavily doped beta-Ga2O3 crystals with 1% Mg, while the UV band, on the contrary, increased and prevailed at low temperatures. Activation energies of separate luminescence bands and conductivity in the investigated crystals are calculated. Some correlations between conductivity and luminescence parameters were found and discussed to give hints for the further development of this material.