The formation and role of the SiO2 oxidation layer in the 4H-SiC/β-Ga2O3 interface

Although 4H-SiC has been regarded as an excellent substrate for the epitaxial growth of β-Ga2O3, an additional oxidation layer could be formed at the substrate during the high temperature growth process. First-principles calculations were employed to investigate the formation and role of the oxidation layer, which was vital for fabricating high quality β-Ga2O3. Through inserting O atoms and emitting CO molecules, the 4H-SiC substrate was spontaneously oxidized, and the oxidation site and process were dependent of the substrate termination. Such inconsistent characters disappeared for the 4H-SiC/β-Ga2O3 interface, and the SiO2 tetrahedron was preferably formed at all the 4H-SiC/β-Ga2O3 interfaces. Moreover, the 4H-SiC/β-Ga2O3 interfaces with Si-terminations and OGa1-termiantions were easier oxidized due to the lower migration energies of O atoms, in particular the O1 atoms. In addition, the oxidization layer accumulated abundant electrons at the SiO2/β-Ga2O3 contact region and turned the type-I band alignment for 4H-SiC/β-Ga2O3 interface into the type-II band alignment, which might be useful to the charge transport of electronic device. However, many interfacial gap states were introduced into the band gaps of 4H-SiC/β-Ga2O3 interfaces, which were harmful to the optoelectronic device.