Iridium-related complexes in Czochralski-grown β-Ga₂O₃

Gallium oxide is a promising semiconductor for its potential as a material in the field of power electronics. The effects of iridium impurities on undoped, Mg-doped, and Ca-doped gallium oxides were investigated with IR spectroscopy. In undoped and Ca-doped β-Ga₂O₃, IR peaks at 3313, 3450, and 3500 cm⁻¹ are tentatively assigned to O–H bond-stretching modes of IrH complexes. Mg-, Ca-, and Fe-doped samples show an Ir⁴⁺ electronic transition feature at 5148 cm⁻¹. By measuring the strength of this feature vs photoexcitation, the Ir^3+/4+ donor level was determined to lie 2.2–2.3 eV below the conduction band minimum. Ga₂O₃:Mg also has a range of sidebands between 5100 and 5200 cm⁻¹, attributed to IrMg pairs. Polarized IR measurements show that the 5248 cm⁻¹ peak is anisotropic, weakest for light polarized along the c axis, consistent with Lenyk et al. [J. Appl. Phys. 125, 045703 (2019)].