Growth condition dependence of photoluminescence of Eu-doped GaN films prepared by radio frequency magnetron sputtering

The Eu-doped GaN thin films (GaN:Eu) were deposited on the c plane of sapphire substrate by the radio frequency magnetron sputtering method. As a target, the GaN compound powder target was used, which contains small amount of EuN powder of 1, 2 and 5 mol%. X-ray diffraction (XRD) and high resolution photoluminescence spectra (PL) of GaN:Eu films were studied with respect to the substrate temperature (300–550 °C). PL spectra exhibited a series of sharp PL lines related to Eu3+ center with intense 622 nm line (dominant PL line for the 5D0–7F2 transition). The PL intensity of the 622 nm line tends to be maximum for 2 mol% EuN in target. The PL intensity tends to be maximum at the substrate temperature of 400–450 °C. This dependence indicated the existence of the optimum temperature at which the formation of the luminescent Eu3+ center is promoted. PL intensity was strongly enhanced by (i) deposition of GaN:Eu on the undoped buffer GaN layers grown on the sapphire substrate and (ii) increase of film thickness.