Local oxidation of InN and GaN using an atomic force microscope

Abstract

Local oxidations of InN and GaN were realized using an atomic force microscope (AFM). InN was oxidized easily by traditional AFM oxidation to ∼40 nm oxide height. The same AFM methodology was applied to GaN, which exhibited only minimum oxidation even at 10 V and high humidity. However, further experimentation led to 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 film reduced the AFM oxidation circuit resistance and increased the oxyanion driving current (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 eliminate this danger, additional experiments were performed in which the gold film on the GaN was removed in a small area, after which AFM oxidation was successfully performed in the area with 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 AFM nano-oxidation for metal–oxide–semiconductor field effect transistors based on two important nitrides.

Evolution of structural defects associated with electrical degradation in AlGaN/GaN high electron mobility transistors

“…One possibility is that oxygen diffuses to cause localized oxidation of the GaN cap under the gate edge, and that this oxide is removed when the sample is exposed to HF, creating the observed grooves. 9,12 However, very shallow indentations were observed in devices stressed below V crit through TEM where no etching process is involved. 13 These grooves are therefore not likely to be a by-product of etching.…”

Enhanced local oxidation of silicon using a conducting atomic force microscope in water

“…6,8,15 By coating the silicon surface with gold, Hwang et al have been able to increase the current flow of the circuit and thereby create oxides of up to 30 nm. 13,16 It has also been shown that increasing the ambient humidity of the system increases the size of the tip-surface capillary bridge and greatly enhances the oxide growth rate by providing a source of oxyanions and improving the conductivity of the circuit. 9,17,18 Nevertheless, the features in Figs.…”

“…The high electric field strength present at the apex of the ultrasharp probe tip induces a local electrochemical oxidation of the surface. A wide variety of surfaces have been modified via tipinduced anodic oxidation, including SiC, 9 GaAs, 10 metals, 11,12 InN, 13 and GaN. 13 These previous studies with Si provide a useful foundation for comparison.…”

“…A wide variety of surfaces have been modified via tipinduced anodic oxidation, including SiC, 9 GaAs, 10 metals, 11,12 InN, 13 and GaN. 13 These previous studies with Si provide a useful foundation for comparison. In the current study, we investigate the possibilities of electrical oxidation experiments performed in water, on both Si/ SiO 2 and Si/ SiO 2 / Au interfaces.…”

Photo-assisted local oxidation of GaN using an atomic force microscope

“…However, GaN and InN are difficult to AFM-oxidize because of high chemical stability. Our studies achieved AFM oxidation of p-type GaN (p-GaN) substrate by using initial deposition of a thin gold layer on the substrate to enhance the initial oxidation current and thus the oxidation rates, producing oxide heights of several tens of nanometres [26], but this technique was debited by intrinsic gold contamination of the oxidized region. Subsequently we found the gold film was necessary only in the immediate vicinity of the region to be oxidized, producing thereby goldfree FM oxidation on p-GaN.…”