Majority site enhancement and increased homogeneity of europium emission in delta-doped gallium nitride

Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications due to its bright red emission and narrow optical linewidths. Such applications demand highly efficient and homogeneous emission, and for this goal it is necessary to optimize the formation of desired Eu incorporation sites and efficient energy transfer into their emissive excited states. In this work, we perform site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating Eu-doped and undoped layers of varying layer thickness. We demonstrate that samples with few-nm-thick doped layers show greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable properties for creating power-efficient LEDs. In a sample with 1nm doped layers, we observe only a single Eu incorporation site, with a narrow, homogeneous emission spectrum that is highly desirable for applications in quantum technologies. This result highlights the potential of delta-doping as a broadly applicable approach to engineering defect properties in rare-earth–doped semiconductors.