Optical properties of β-Ga2O3 and α-Ga2O3:Co thin films grown by spray pyrolysis

Abstract

Stable β‐Ga₂O₃ and α‐Ga₂O₃:Co thin films were grown on thoroughly cleaned borosilicate glass plates by the spray pyrolysis method. The substrate temperature during growth was maintained at 350 °C and the film was then annealed in air at 350 °C for 30 min. The optical energy gaps for these films at 295 K was given as 4.23 eV for β‐Ga₂O₃ and 2.41 eV for α‐Ga₂O₃:Co. The impurity absorption peaks for α‐Ga₂O₃:Co thin film due to the transitions of ⁴A₂(⁴F)→⁴T₁(⁴P), ⁴A₂(⁴F)→⁴T₁(⁴F), and ⁴A₂(⁴F)→⁴T₂(⁴F) of Co²⁺ ions were observed at 14 925, 7142, and 4166 cm⁻¹, with Racah parameters given as Dq=416 cm⁻¹ and B=638 cm⁻¹.