Luminescence spectroscopy of Cr3+ ions in bulk single crystalline β-Ga2O3

Detailed investigations of the spectroscopic properties of Cr(3+)ions in beta-Ga2O3:0.05% Cr(3+)single crystals grown by the floating zone technique have been performed in the temperature range 4.5-550 K. The luminescence of Cr(3+)ions at low temperatures is due to narrow R-lines (E-2 ->(4)A(2)transitions) and their vibronic sidebands, whereas the broad intense band (T-4(2)->(4)A(2)transition) dominates at temperatures above 200 K. The vibronic sidebands of R-lines with amplitude of less than 5% of the R-1-line at a temperature of 4.5 K cover the region of 700-735 nm. The temperature dependences of the luminescence intensity and the decay time of Cr(3+)ions indicate the same mechanism of quenching of R-line intensity and shortening of lifetime for(2)E of Cr(3+)ions. The temperature dependence of the R-1-line decay time of beta-Ga2O3:Cr(3+)with maximal temperature coefficient vertical bar Delta tau/Delta T vertical bar = 0.023 ms K(-1)at 120 K and maximal specific sensivitity vertical bar(Delta tau/Delta T)tau(-1)vertical bar = 0.017 K(-1)at 160 K indicates an application potential of this phosphor for low-temperature fluorescence thermometry.