Simulations and Experimental Results of Color-Tunability in Eu-doped GaN LEDs

The rare-earth ion Eu³⁺ is well-known for its red emission at ~620 nm; however, green emission at ~545 nm also exists and is significant in Eu-doped GaN-based devices under certain current injection conditions. The relative change of intensity in the red and green emission peaks of these LEDs allows for color tuning of the overall emission, which is facilitated by pulsed current injection at various frequencies and duty cycles. This result makes the Eu-doped GaN LED an ideal candidate for a color-tunable single pixel, which could be useful for advancements in micro-LED display applications. The change in the relative emission intensity results from changes in the population ratio between the ⁵D₀ and ⁵D₁ excited states of the Eu³⁺ ions. A series of rate equations, which models each state's population, was used to explore the color tuning possibilities under different current injection conditions. Emission spectra from fabricated devices were collected under these current injections conditions, and the experimental results were compared with the simulations.