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 -Ga 2 O 3 ) thin films are investigated. Second phase formation ( γ -Ga 2 O 3 ) is observed due to implantation-induced damage of the β -Ga 2 O 3 lattice. Annealing the implanted films results in various β -Ga 2 O 3 grain orientations. The relationship between the crystalline nature and the optical properties of the β -Ga 2 O 3 :Gd 3 + 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 6 P 7 / 2 → 8 S 7 / 2 transition of Gd 3 + in β -Ga 2 O 3 . Its four constituent emission components at 3.9118 eV, 3.9153 eV, 3.9221 eV and 3.9348 eV, due to the ion’s 6 P 7 / 2 Stark splitting in the β -Ga 2 O 3 crystal field, are investigated. The transition energies are independent of annealing temperature and film growth method, highlighting the insensitivity of the 4f 7 orbital to minor changes in the monoclinic crystal environment. • MBE- and ALD-grown gallium oxide thin films are implanted with gadolinium. • Four UV-B PL peaks from the Stark-split 6 P 7 / 2 level of Gd 3 + are individually resolved. • A higher UV-B PL intensity is correlated to crystalline order over a longer range. • The PL peaks from the 6 P 7 / 2 → 8 S 7 / 2 transition exhibit FWHM down to 0.9 meV. • Measured emission energies independent of growth method and implantation parameters.