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-degrees-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 t op 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. How ever, 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 .