Stark manifold ultraviolet emission in Gd-implanted β -Ga 2 O 3 thin films

Gadolinium (Gd) is a promising optically active lanthanide for UV emission. In this work, the optical emission properties of Gd-implanted monoclinic gallium oxide (β-Ga2O3) thin films are investigated. Second phase formation (γ-Ga2O3) is observed due to implantation-induced damage of the β-Ga2O3 lattice. Annealing the implanted films results in various β-Ga2O3 grain orientations. The relationship between the crystalline nature and the optical properties of the β-Ga2O3:Gd3+ films is studied. Optical activation occurs after annealing at 700°C, revealing a photoluminescence (PL) band at 3.92 eV. This emission is attributed to the 6P7∕2 → 8S7∕2 transition of Gd3+ in β-Ga2O3. Its four constituent emission components at 3.9118 eV, 3.9153 eV, 3.9221 eV and 3.9348 eV, due to the ion’s 6P7∕2 Stark splitting in the β-Ga2O3 crystal field, are investigated. The transition energies are independent of annealing temperature and film growth method, highlighting the insensitivity of the 4f7 orbital to minor changes in the monoclinic crystal environment.