Sol-gel derived phase pure α-Ga2O3 nanocrystalline thin film and its optical properties

Single-phase α-Ga2O3 thin films in the nanocrystalline form were prepared by the sol-gel technique. The optimum annealing temperature was found to be 500 °C. Below this temperature, a mixed phase of α-GaO(OH) and α-Ga2O3 was found and above this range a mixed phase of α-Ga2O3 and β-Ga2O3 was detected. A pure β-phase was observed at higher annealing temperatures. The crystallite size of α-Ga2O3 was found to be about 16 nm. The optical band gap of α-Ga2O3, determined from transmittance measurements, was found to be 4.98 eV which was higher than that of the β-phase prepared in identical condition. The semiconducting transition of this phase was allowed direct type like β-phase.