Microstructure of oxidized layers formed by the low-temperature ultraviolet-assisted dry oxidation of strained Si0.8Ge0.2 layers on Si

Ultraviolet-assisted low-temperature (550 °C) dry oxidation of Si0.8Ge0.2 strained layers on (100)Si has been studied. The oxidation rate of this material was found to be a factor of 2 greater than that of pure Si oxidation under identical irradiation conditions. Initially, the structure of the oxidized material consists of a SiO2 layer on top of a strained Si1−xGex layer with a Ge concentration significantly higher (x≳0.2) than the initial value. Increasing the oxidation time produces more SiO2 and a Si1−xGex layer further enriched with Ge. However, the oxidation rate is reduced and some of the Ge becomes trapped inside the growing SiO2 layer. For a prolonged irradiation time (≳5 h) SiGe oxidation still continues, unlike the case for pure Si, while the Ge trapped inside the SiO2 forms isolated microcrystalline regions.