Effects of Mg-codoping on the 1540-nm photoluminescence of Er-implanted GaN

The ∼ 1540-nm Er³⁺ photoluminescence (PL) and photoluminescence excitation (PLE) spectra of Er-implanted Mg-codoped GaN (GaN:Er+Mg) indicate that the excitation efficiency of a specific Er³⁺ center among different Er³⁺ centers existing in Er-implanted GaN is selectively enhanced, compared to Er-implanted undoped GaN (GaN:Er). In GaN:Er+Mg, the 1540-nm PL peaks characteristic of the so-called "violet-pumped" Er³⁺ center and the ∼ 2.8-3.4 eV (violet) PLE band are significantly strengthened by the Mg-doping. The intra-f absorption PLE bands associated with this "violet-pumped" center are also enhanced by this doping. The 1540-nm PL peaks originating from the "violet-pumped" center dominate the above-gap-excited Er³⁺ PL spectrum of GaN:Er+Mg whereas they are unobservable under above-gap excitation in GaN:Er. All of these results indicate that Mg doping increases the efficiency of trap-mediated excitation of Er³⁺ emission in Er-implanted GaN.