Effects of growth temperature on phase transformation and crystal quality of Ga2O3 films grown on Si/AlN composite substrates by MOCVD

Abstract

High-quality ε-phase Ga2O3 thin film with a FWHM of 0.68° for the (002) plane in omega scan is grown on Si/AlN composite substrate by MOCVD. The crystal phase evolution and microstructure of Ga2O3 thin films at different temperatures are studied systematically. It is found that Ga2O3 changes from amorphous at 400 °C to ε-phase at 500 °C. As the temperature further rises to 600 °C, it eventually transforms into β-phase. Due to the difference of lattice mismatch, ε-Ga2O3 is crystalline with high crystallinity on the surface of the film, but amorphous at the interface, while β-Ga2O3 is polycrystalline. In addition, ε-Ga2O3 thin films not only have the smoothest surface with roughness of 2.63 nm, but also the content of point defects (such as oxygen vacancies) is significantly reduced compared with that of amorphous and β-Ga2O3 thin films. This work provides important references for the hetero-integration of Si and Ga2O3 by MOCVD, and is beneficial for the development of low cost and high crystal quality Ga2O3 thin films which are suitable for high voltage and ultraviolet optoelectronics.