Development of site-selective doping of rare-earth into nitride semiconductor

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Eu doped nitride semiconductor is a hopeful material for realizing a novel device with unique features, such as narrow spectra, and no temperature dependence of emission wavelength. However, not all Eu ions incorporated in GaN host are optically active, resulting in reduction of emission efficiency. This is due to that the local crystal structure around Eu ion strongly affects energy transfer and luminous efficiency. In this study, we found Mg codoping technology and succeeded to improve emission efficiency by controlling optical site. For PL measurement, three strong peaks corresponded to ^5D_0-^7F_2 transitions were observed. With increasing Mg concentration, the dominant peak wavelength changed from 622.3 to 620.3 nm. The PL integrated intensity of the sample with optimal Mg concentration was 20 times higher than that of the sample without Mg co-doping. For the optimal sample, the luminous efficiency was estimated to be 77%. These results indicated that Mg co-doping could control the optical sites in GaN and led to suppress the non-radiative component from 5D0 level.