Formation of a Ge-rich layer during the oxidation of strained Si _1-xGe_x

The diffusion of Ge in Ge-rich layer (GRL) and the factors affecting on it during the oxidation of strained Si_1-xGe_x layers were examined. Strained Si_1-xGe_x layers, having different initial Ge concentrations (x=0.15 and 0.3), were oxidized at 800 and 900°C in a dry O₂ ambient for different oxidation times. The diffusion of Ge into the underlying Si_1-xGe_x layer having an initial constant composition and the resulting transformation to GRL were both enhanced with an increase in oxidation temperature. After complete transformation to GRL, GeO₂ started to become incorporated into the resulting oxide layer. The formation of GeO₂ was initiated by the Ge saturation of the GRL layer with Ge and by the differences in diffusivity of Ge atoms in Si _1-xGe_x and Si substrate. The relaxation occurred when the Ge concentration in the GRL reached a critical value and was not affected by either oxidation time or temperature.