Growth mechanism and characteristics of β-Ga2O3 heteroepitaxailly grown on sapphire by metalorganic chemical vapor deposition

In this study, monoclinic gallium oxide (β-Ga2O3) epilayer was successfully grown on c-plane, (0001), sapphire substrate by metalorganic chemical vapor deposition (MOCVD) with interplaying growth temperature, TEGa flow rate, and growth time. X-ray diffraction 2θ scans show only three narrow diffraction peaks referred to β-Ga2O3(2¯ 01), (4¯ 02), and (6¯ 03) in all epilayers, indicating a superior crystalline quality. Current-voltage (I–V) measurement reveals that these β-Ga2O3 films are insulating and exhibit high resistance in a range of 1012–1014 Ω. The crystallization characteristics of the epilayers can be effectively improved with thickness through increasing TEGa flow rate and growth time, which was evidenced by X-ray rocking curves and I–V measurements. However, the surface roughness of β-Ga2O3 film increases with growth time and TEGa flow rate. When the growth temperature increases above 825 °C, the thickness of β-Ga2O3 film decreases clearly. Furthermore, it can be found that the growth rate decreased as the growth time increasing. The growth mechanism based on first-principles calculation was proposed as that 3D growth induced by the lattice mismatch between β-Ga2O3 and sapphire starts at nucleation stage, and follows up a lateral growth promoting a 2D growth after the thick epilayer being grown. In addition, the complex chemical reaction between TEGa and oxygen precursors was unraveled by density function theory calculation.