Strong enhancement of red photoluminescence from Eu doped Ga2O3 films by thermal annealing

Eu doped Ga2O3 thin films were prepared by pulsed laser deposition on sapphire substrates. The influences of thermal annealing temperature as well as the annealing ambient on the optical and structural properties of Ga2O3:Eu were investigated by means of photoluminescence (PL), X-ray diffraction, and Raman measurements. The PL spectra reveal that the thermal annealing treatment in an oxygen ambient at 600 °C results in a remarkable 10-fold enhancement in the Eu-related red luminescence by contrast to the as-grown Ga2O3:Eu sample. The comparison of PL spectra for films annealed under different ambient confirms that the strong enhancement in the Eu-related luminescence is correlated with the oxygen, which can greatly reduce the defects and suppress the nonradiative recombination paths. Moreover, Ga2O3:Eu films with higher Eu concentrations exhibit stronger PL enhancement compared to the samples with lower Eu doping levels, providing an effective method to suppress the concentration quenching effect. We anticipate that this study paves the way towards highly efficient red light-emitting devices based on Ga2O3:Eu films.