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

In this work, H₂O-Al₂O₃/O₃-Al₂O₃ insulating bilayers were grown on GaN by atomic-layer deposition (ALD) technique using H₂O vapor and O₃ as oxidants. The electrical and material properties show that the H₂O-Al₂O₃/O₃-Al₂O₃ 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 H₂O-Al₂O₃ interlayer between the O₃-Al₂O₃ 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 Al₂O₃/GaN interface reduced, while increasing the thicknesses of the H₂O-Al₂O₃ interlayer restricted the 'V_th shift' phenomenon and improved the stability and reliability of the GaN MOS devices. [ABSTRACT FROM AUTHOR]