Investigation of O_3-Al_2O_3/H_2O-Al_2O_3 dielectric bilayer deposited by atomic-layer deposition for GaN MOS capacitors

摘要

In this work, H_2O-Al_2O_3/O_3-Al_2O_3 insulating bilayers were grown on GaN by atomic-layer deposition (AI..D) technique using H_2O vapor and O_3 as oxidants. The electrical and material properties show that the H_2O-Al_2O_3/O_3-Al_2O_3 stack structure appealed 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_2O-Al_2O_3 interlayer between the O_3-Al_2O_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_2O_3/GaN interface reduced, while increasing the thicknesses of the H_2O-Al_2O_3 interlayer restricted the "V_(th) shift" phenomenon and improved the stability and reliability of the GaN MOS devices.