Reverse temperature dependence of Ge surface segregation during Si-molecular beam epitaxy

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Abstract
Ge surface segregation on Si(100) and Si(111) substrates during silicon molecular beam epitaxy was studied using x-ray photoelectron spectroscopy. During growth, the Ge atoms were only partly incorporated into the growing layer and the residuals segregated on the grown surface. The Ge segregation phenomena increased to a maxima at around 450 °C in the case of the Si(100) substrates and at around 650 °C in the case of the Si(111) substrates. Segregation decreased above these temperatures. These reverse temperature dependencies enable not only good crystallinity of the heteroepitaxial layer, but also abrupt heterointerfaces. The incorporation coefficients for Si(111) were much larger than those for Si(100), which is well explained by a model based on surface migration.