Ga-doping effects on electrical and luminescent properties of ZnO:(La,Eu)OF red phosphor thin films

Red thin-film phosphors were fabricated based on a ZnO:(La,Eu)OF nanocomposite structure where (La,Eu)OF nanoparticles were dispersed in a ZnO film matrix. The films were deposited on glass substrates by a sol-gel method at a low temperature of 600 °C using trifluoroacetic acid as a fluorine source. Doping gallium into the films suppressed the grain growth of ZnO, increased the optical band gap, and decreased electrical resistivity, which indicates that Ga3+ was selectively incorporated into the ZnO lattice. Eu3+ was practically doped in the LaOF lattice. As a result, strong red emissions due to the D05→F27 transition of Eu3+ were observed in both photo- (PL) and cathodoluminescence (CL) measurements. The efficiency of ultraviolet light excitation at 274 nm was promoted by the charge transfer from O2− to Eu3+ in PL. Ga doping was found to increase the CL intensity of the film, which was attributed to suppression of charge accumulation on the films.