Growth of polycrystalline gallium oxide films in stagnant oxygen stream ambient

Structural, morphological, optical, and electrical characteristics of polycrystalline gallium oxide (Ga2O3) films subjected to different post-deposition annealing temperatures (400–1000 °C) in a stagnant oxygen stream ambient were systematically studied. The transformation from γ-Ga2O3 to β-Ga2O3 phase was perceived as the temperature was enhanced to/beyond 600 °C. An alleviation of oxygen related defects in Ga2O3 films was supported through a reduction in full-width half maximum (FWHM) for β-Ga2O3 peak oriented in (400) plane and dislocation density (δ), as well as an improvement in crystallinity when a higher temperature was employed. Nonetheless, the employment of the highest temperature has contributed to an excessive diffusion of oxygen anions to the interface contributing to the formation of a well-defined interfacial layer. Besides, the oxygen ions were also occupying the interstitial sites of Ga2O3 lattice at 1000 °C contributing to a sudden contraction of indirect band gap (Eg). These detrimental effects have suggested that 1000 °C was not a suitable annealing temperature for Ga2O3 films. Of these investigated films, Ga2O3 film annealed at 800 °C has demonstrated a better leakage current density characteristic than that of 400 and 600 °C due to acquisition of the lowest δ, the smallest FWHM, as well as the largest direct and indirect Eg.