Current-injection electroluminescence from Pr-related centers in an ion-implanted GaN diode structure

We report room-temperature current-injection electroluminescence (EL) from praseodymium (Pr)-related centers in an ion-implanted gallium nitride (GaN) diode structure. Pr ions were introduced into GaN by ion implantation, and the samples were subsequently subjected to ultrahigh-pressure annealing (UHPA) and metal organic vapor phase epitaxy regrowth to form the p-side layers. Under forward bias, a narrow EL peak at 652 nm was observed. This peak coincides with the Pr-related photoluminescence (PL) peak, indicating that Pr-related centers remain optically active after ion implantation, UHPA, regrowth, and device fabrication and can be electrically excited in the processed GaN structure. Secondary ion mass spectrometry and current density–voltage (J–V) measurements reveal pronounced structural and electrical nonidealities in the fabricated structure, including displacement of the effective junction/interface positions from the target design, impurity redistribution near the regrown region, leakage-related transport, and a large apparent turn-on voltage. The optical data therefore indicate that a Pr-related emission process exists under nonideal current injection, while its efficiency is limited by parasitic current paths, nonradiative losses, and the limited availability of local configurations and defect-related states that enable efficient host-to-Pr energy transfer. The saturation-like behavior of the Pr-related EL, together with the simultaneous increase in near-band-edge and Mg-related emission at higher current densities, suggests that additional current does not proportionally enhance the Pr-related emission but increasingly produces radiative recombination from the GaN host and Mg-related states. These results clarify the excitation and limitation mechanisms of Pr-related EL in ion-implanted GaN diode structures and identify requirements for future electrically driven lanthanoid emitters in GaN.