Investigation of O₃‐Al₂O₃/H₂O‐Al₂O₃ dielectric bilayer deposited by atomic‐layer deposition for GaN MOS capacitors

Abstract

In this work, H 2 O‐Al 2 O 3 /O 3 ‐Al 2 O 3 insulating bilayers were grown on GaN by atomic‐layer deposition (ALD) technique using H 2 O vapor and O 3 as oxidants. The electrical and material properties show that the H 2 O‐Al 2 O 3 /O 3 ‐Al 2 O 3 stack structure appeared to be an appropriate dielectric for GaN MOS devices that had low leakage current densities, high breakdown voltages, and good capacitance–voltage ( C–V ) curves. The H 2 O‐Al 2 O 3 interlayer between the O 3 ‐Al 2 O 3 and GaN efficiently prevented the GaN surface from oxidizing by ozone oxidant by its strong oxidizing power. By taking photo‐assisted C–V measurements, it was found that the deep interface state densities at the Al 2 O 3 /GaN interface reduced, while increasing the thicknesses of the H 2 O‐Al 2 O 3 interlayer restricted the “V th shift” phenomenon and improved the stability and reliability of the GaN MOS devices.