The oxidation of amorphous Si0.65Ge0.27C0.08 and single-crystal Si0.63Ge0.36C0.01 in wet ambient at 700 and 900°C has been studied using Rutherford backscattering spectrometry and transmission electron microscopy. A reference sample of Si0.63Ge0.37 was also oxidized in order to determine the influence of carbon on the oxidation behavior. The low C content alloy behaved similar to the SiGe alloy: uniform Si1-xGexO2 was obtained at 700°C whereas SiO2 was formed at 900°C, and Ge piled up underneath the oxide. In both cases, carbon was not detected in the oxide layer. The amorphous Si0.65Ge0.27C0.08 alloy behaved significantly different at both oxidation temperatures in comparison with the crystalline Si0.63Ge0.36C0.01 and Si0.65Ge0.37. Negligible oxidation occurred at 700°C whereas SiO2 was obtained at 900°C and the rejected Ge distributed uniformly throughout the SiGeC alloy. It is proposed that fast Ge diffusion during oxidation at 900°C resulted from diffusion at grain boundaries, since crystallization of the amorphous SiGeC layer occurred in conjunction with oxidation, leading to nucleation of nanocrystals (∼5 nm diam). The oxidation/annealing treatment has thus provided a useful mechanism for increasing the relative Ge concentration in the SiGeC alloy.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)