Effects of growth pressure on the characteristics of the β-Ga2O3 thin films deposited on (0001) sapphire substrates

Abstract β-Ga2O3 films were grown on (0001) sapphire substrates by low-pressure MOCVD. The effects of growth pressure on the growth rate, surface morphology and optical properties of β-Ga2O3 thin films were investigated. XRD showed that the β-Ga2O3 films grown preferentially along the (-201) crystal plane family were obtained, and the increase in growth pressure led to a decrease in growth rate, consistent with the SEM results. AFM measurements indicated that the increase in growth pressure reduced the grain size and RMS roughness. Optical transmission spectroscopy demonstrated that the average transmittance of all films in the visible range exceeded 75%, and the optical bandgap at 20, 30 and 40 Torr were 4.95, 4.93 and 4.91 eV, respectively. XPS revealed that the Ga 2p peak and O 1s peak blue shift as the growth pressure. Through RT-Raman spectroscopy, the low-frequency and high-frequency Raman vibration modes of β-Ga2O3 were detected.