Temperature dependence of energy transfer mechanisms in Eu-doped GaN

The temperature dependent behavior of continuous-wave and time-resolved photoluminescence of Eu-doped GaN in the visible region is measured for both the ${}^5{D}_0{\to }^7{F}_2$ and ${}^5{D}_0{\to }^7{F}_3$ transitions. The radiative decay of these transitions, following pulsed laser excitation of the GaN host, is monitored by a grating spectrometer and photomultiplier tube detector system. In addition to these two radiative energy transfer pathways within ${\mathrm{Eu}}^{\text{3+}},$ the data reveal two nonradiative energy transfer paths between ${\mathrm{Eu}}^{\text{3+}}$ and the host GaN. Decay constants for the relaxation processes are extracted from the data using a numerically solved rate equation model. Although the dominant radiative relaxation processes decayed with a temperature insensitive decay constant of 166 μs, a prominent role for nonradiative transfer between ${\mathrm{Eu}}^{\text{3+}}$ and impurities within the GaN host was deduced above 180 K.