Undoped β-Ga2O3 layer thickness effect on performance of MOSFETs grown on sapphire substrate

β-Ga2O3 MOSFETs with various un-intentionally doped (UID) layer thicknesses of (2 ̅01) beneath the Si doped film were grown by metalorganic chemical vapor deposition on a (0001) sapphire substrate. The UID layer thickness gives rise to MOSFET turn-on current increasing, Ron decreasing and breakdown voltage decreasing. Through X-ray photoelectron spectroscopy (XPS) we ascribe this increased turn-on current and reduced breakdown voltage to oxygen vacancies.