Efficient relaxation of strained-SiGe layers induced by thermal oxidation

The new route to fabricate compositionally graded and highly-relaxed Si1-xGex layers using thermal oxidation at high temperatures is investigated. Ge atoms behavior during thermal oxidation of Si1-xGex layers is strongly dependent on the oxidation temperature. For low temperature oxidation processes Ge is incorporated as GeO2 in the grown oxide layer, while for higher temperatures it accumulates below the grown oxide into a layer with a higher concentration than the initial Si1-xGex. However, Si1-xGex layers oxidized at 1000 °C did not show such an accumulation layer because Ge diffusion efficiently occurred, resulting in the formation of a compositionally graded and relaxed Si1-xGex layer. Such layers could be used as virtual substrates for the strained-Si and relaxed-SiGe applications.