Growth of "oxide-less" GaN layer by helicon-wave excited N-2-Ar plasma treatment of Al/GaAs structure

Gallium nitride could be formed by direct nitridation of GaAs using the hel icon-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 excite d N-2-Ar plasma. X-ray photoelectron spectroscopic measurements were perfor med 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 Al2O3 and AIN were formed. Under the Al2O3-AIN mixed film , a GaN layer was uniformly formed on GaAs;. Oxides of Ga and As, such as G a2O3, GaO, As2O3 and AsO were scarcely observed in the film. Thus, an "oxid e-less" GaN layer was obtained. However, a small amount of elemental arseni c was detected in the GaN layer. Nitrogen atoms or ions are considered to d iffuse 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.