Low leakage current β-Ga₂O₃ MOS capacitors with ALD deposited Al₂O₃ gate dielectric using ozone as precursor

Abstract Metal–insulator–semiconductor (MOS) capacitor is a key structure for high performance MOS field transistors (MOSFETs), requiring low leakage current, high breakdown voltage, and low interface states. In this paper, β -Ga 2 O 3 MOS capacitors were fabricated with ALD deposited Al 2 O 3 using H 2 O or ozone (O 3 ) as precursors. Compared with the Al 2 O 3 gate dielectric with H 2 O as ALD precursor, the leakage current for the O 3 precursor case is decreased by two orders of magnitude, while it keeps the same level at the fixed charges, interface state density, and border traps. The SIMS tests show that Al 2 O 3 with O 3 as precursor contains more carbon impurities. The current transport mechanism analysis suggests that the C–H complex in Al 2 O 3 with O 3 precursor serves as deep energy trap to reduce the leakage current. These results indicate that the Al 2 O 3 / β -Ga 2 O 3 MOS capacitor using the O 3 precursor has a low leakage current and holds potential for application in β -Ga 2 O 3 MOSFETs.