Suppression of Parallel Conduction at the Interface in β-Ga₂O₃ Homoepitaxial Layer Using Semi-Insulating Intermediate Layer

β-Ga₂O₃ is one of the wide-gap semiconductors investigated actively in recent years, and evaluation of its electrical properties is needed for various device applications. However, the presence of Si impurity on a β-Ga₂O₃ substrate has been a tantalized issue, which gives rise to parasitic conduction parallel to the interface with an overgrown epilayer. Therefore, this interface conduction must be eliminated in order to measure the electrical characteristics inherent in the epilayers. Using pulsed-laser deposition, we revealed that a semi-insulatiug β-Ga₂O₃:Fe intermediate layer, as thin as 7 nm, was effective to passivate the Si impurity and the interface conduction became negligibly low. Moreover, we achieved room-temperature Hall mobility as high as 28 cm²V^-1s^-1 for the β-Ga₂O₃:Si film grown on the intermediate layer. These results demonstrate a facile route to access fundamental electrical properties of homoepitaxial β-Ga₂O₃ films.