Transition from thin film to nanostructure in low pressure chemical vapor deposition growth of β-Ga2O3: Impact of metal gallium source

Highly crystalline beta-Ga2O3 has been grown on a c-plane (0001) sapphire substrate using low-pressure chemical vapor deposition. This work has been focused on the impacts of the Gallium (Ga) concentration on the surface morphology of the beta-Ga2O3 films. Formation of thin film, nanostructure, and the combination of both have been observed. However, no changes have been noticed on the X-ray diffraction peaks of beta-phase with an increase in Ga vapor concentration, though different crystal orientation of the nanostructures has been found in the sample with relatively high Ga amount. The average crystallite size which has been calculated using Scherrer's formula shows an increment with Ga concentration. The bandgap has also been found to be altered with the metal concentration. The crystal quality of the nanostrctures evaluated from the Raman measurements shows good quality with low internal strain and low defects density. A small amount of Ga will tend towards the thin film growth whereas a high amount of Ga leads to the formation of different types of nano-structure on the beta-Ga2O3 thin film. We propose that the nanostructures are formed through vapor-solid and vapor-liquid-solid mechanisms under the self-catalytic approach.