Partially strained Si1-xGex/Si structures investigated by photoreflectance spectroscopy

Partially strained Si1-xGex epilayers with germanium composition up to 25% have been studied by room temperature photoreflectance spectroscopy. Observed transitions were identified as E1 and E0' direct transitions at Si1-xGex structure. The E1 transition energy dependence on alloy composition shows that the studied Si1-xGex epilayers are partially relaxed and the degree of relaxation differ from one structure to another. For the germanium content close to 10% the crossing between E1 and E0' optical transitions was observed.