Growth of "Oxide-Less" GaN Layer by Helicon-Wave Excited N_2-Ar Plasma Treatment of Al/GaAs Structure

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Gallium nitride could be formed by direct nitridation of GaAs using the helicon-wave excited N_2-Ar plasma at or near the grown insulative layer/GaAs interface. However, a fair amount of the oxides and the suboxide of Ga and As also existed in this insulative layer. In the present study, the Al/GaAs(100)structure, instead of a GaAs one, was exposed to the heliconwave excited N_2-Ar plasma. X-ray photoelectron spectroscopic measurements were performed to investigate the chemical composition and depth profile of the grown layer. The top Al film was completely nitrided and oxidized (due to residual oxygen), so that Al_2O_3 and AlN were formed. Under the Al_2O_3-AlN mixed film, a GaN layer was uniformly formed on GaAs. Oxides of Ga and As, such as Ga_2O_3, GaO, As_2O_3 and AsO were scarcely observed in the film. Thus, an "oxide-less" GaN layer was obtained. However, a small amount of elemental arsenic was detected in the GaN layer. Nitrogen atoms or ions are considered to diffuse into the Al film and react with GaAs to produce GaN. The presence of the grain boundaries in "Al" enhances the N_2 diffusion. The oxides of Ga and As were probably eliminated by the reducing effect of Al.
社団法人応用物理学会の論文
1999-04-15