Local oxidation of InN and GaN using an atomic force microscope

Abstract

Local oxidations of InN and GaN were realized using an atomic forcemicroscope (AFM). InN was oxidized easily by traditional AFM oxidation to∼40 nm oxide height. The same AFM methodology was applied to GaN, which exhibited onlyminimum oxidation even at 10 V and high humidity. However, further experimentation ledto successful nano-oxidation of GaN by two different techniques. In the first technique, a∼10 nm gold film was deposited by sputtering onto the clean GaN substrate. The gold filmreduced the AFM oxidation circuit resistance and increased the oxyanion drivingcurrent (oxidation current), thereby allowing AFM oxidation with heights reaching∼25 nm at a humidity of 70%, but with a danger of gold contamination of the oxide. To eliminatethis danger, additional experiments were performed in which the gold film on the GaN wasremoved in a small area, after which AFM oxidation was successfully performed in the areawith gold removed with oxidation heights comparable to those of the gold-covered GaN.The techniques in this study make possible fast, chemical-free and contamination-free AFMnano-oxidation for metal–oxide–semiconductor field effect transistors based on twoimportant nitrides.