GaN-Based White-Light-Emitting Diodes Fabricated with a Mixture of Ba₃MgSi₂O₈:Eu²⁺ and Sr₂SiO₄:Eu²⁺ Phosphors

Abstract

The photoluminescence (PL) spectra of Ba 3 MgSi 2 O 8 :Eu 2+ show one peak at 442 nm and two unresolved peaks at 505 nm. The 442 nm peak is attributed to the 4f→5d transition of the Eu 2+ ion doped in the Ba 2+ (I) site with a weak crystal field, while the 505 nm peak originates from Eu 2+ ions on the Ba 2+ (II) or the Ba 2+ (III) site with a strong crystal field. The PL spectra of the Sr 2 SiO 4 :Eu 2+ show two emission peaks at 470 nm and 560 nm. The emission intensity at 470 nm decreases with increasing Eu 2+ concentration, while that at 560 nm increases. This can be understood by considering the energy transfer from the 470 nm band to the 560 nm band through multipolar interaction. The GaN-based white-light-emitting diode (LED) fabricated using a mixture of Ba 3 MgSi 2 O 8 :Eu 2+ and Sr 2 SiO 4 :Eu 2+ phosphors has a broad-band spectrum, higher color rendering index and higher color stability against forward bias currents than Y 3 Al 5 O 12 :Ce 3+ -based white-LEDs.