Annealing temperature controlled crystallization mechanism and properties of gallium oxide film in forming gas atmosphere

Abstract Gallium oxide (Ga 2 O 3 ) films had been fabricated on Al 2 O 3 (0001) substrate by employing pulsed laser deposition (PLD) and annealed at different temperatures under forming gas (FG) atmosphere (95% N 2 + 5% H 2 ). The influence of annealing temperature on the structural, optical, chemical composition, and surface morphological properties of the Ga 2 O 3 thin films was investigated comprehensively. The annealing processes with hydrogen gas play a crucial role in the characteristics of Ga 2 O 3 thin films. A crystallization mechanism of Ga 2 O 3 films controlled by annealing temperature has been proposed firstly and analyzed systematically, which contains three kinds of competitive mechanism, namely the thermal enhanced crystallization, the enhanced H 2 dissociative adsorption on Ga 2 O 3 surfaces, and the high‐temperature decomposition of Ga 2 O 3 . Both Ga + and Ga 3+ oxidation valence states were presented in all samples, which indicated lattice oxygen deficiency in Ga 2 O 3 films. The variation of the non‐lattice oxygen proportion of Ga 2 O 3 films related to the crystallization mechanism firstly increased and then decreased with the increase of annealing temperature. The detailed crystallization mechanism of PLD‐Ga 2 O 3 films annealed in FG offers a guideline and references for the further fabrication of high‐quality Ga 2 O 3 films and their applications in high‐performance devices.