Zinc–hydrogen and zinc–iridium pairs in β-Ga₂O₃

Zinc-doped monoclinic gallium oxide (β-Ga₂O₃:Zn) has semi-insulating properties that could make it a preferred material as a substrate for power devices. Infrared and UV/Visible spectroscopy were used to investigate the defect properties of bulk β-Ga₂O₃:Zn crystals. As-grown crystals contain a single O-H stretching mode at 3486.7 cm⁻¹ due to a neutral ZnH complex. A deuterium-annealed sample displays the corresponding O-D stretching mode at 2582.9 cm⁻¹, confirming the O-H assignment. A strong Ir⁴⁺ electronic transition at 5147.6 cm⁻¹ is also observed, along with sidebands attributed to ZnIr pairs. These sidebands show distinct differences compared with Mg-doped samples; most importantly, several peaks are attributed to Ir⁴⁺ paired with a Zn on the tetrahedral Ga(I) site. Annealing under an oxygen atmosphere produced an insulating material with a resistance above 1 TΩ.