Heteroepitaxial growth of α-Ga2O3 thin films on a-, c- and r-plane sapphire substrates by low-cost mist-CVD method

Abstract α-Ga2O3 has received wide attention as a wide bandgap semiconductor. Many reports have reported heterogeneous epitaxial growth of α-Ga2O3 thin films, which basically use c-plane (0006) sapphire as a substrate. However, research on the growth of α-Ga2O3 on substrates such as a-, r-plane sapphire is still lacking. This paper systematically analyzes the differences of α-Ga2O3 films grown on different sapphire substrates (a-, c- and r-plane) using the non-vacuum, highly scalable and low-cost mist-CVD method. The in-plane and out-of-plane orientations of all three samples were consistent with their substrates. A series of complementary measurements (XRD, XPS, AFM, TEM, and UV-Vis) were used to characterize the crystallinity, elemental composition, surface morphology, lattice structure, growth rate, and optical bandgap of the α-Ga2O3 grown on substrates of different plane. It is shown that compared to the samples on other two plane substrates, the c-plane α-Ga2O3 films has a smallest FWHM of 0.204°, an ideal band gap width of 5.29 eV, a small Root-Mean-Square (RMS) of 1.64 nm, a growth rate of 11.44 nm/min and a perfect lattice structure among all the three samples. Thus, the c-plane sapphire is more suitable for high-quality α-Ga2O3 growth compared to the other plane substrates.