Investigation of optical gain in Eu-doped GaN thin film grown by OMVPE method

We prepare and optically characterize a thin film of GaN:Eu. Room temperature intense emission band at around 620 nm is observed, corresponding to ⁵D₀ → ⁷F₂ electronic dipole transition of Eu³⁺ ions in the GaN host material. At lower temperatures, three components, at 621, 622, and 623 nm, arising from different Eu³⁺ optical centers, can be distinguished. Using a combination of variable stripe length (VSL) and shifting excitation spot (SES) methods we investigate optical gain of this Eu-related PL band at room temperature and determine its lower limit to be approximately 14 cm⁻¹.