Impact of the SiGe/Si interface structure upon the low temperature photoluminescence of a Si/Si1−xGex multiple quantum well

The effect of interfacial potential fluctuations of a Si/SiGe multiple quantum well structure upon the low-temperature exciton luminescence is reported. Exciton localisation at such potential fluctuations with a lateral period of 4–6 nm is observed as a strong blue-shift in the power dependence of the low-temperature photoluminescence (PL). To characterise the structure of the interfaces, X-ray diffraction and reflectivity, X-ray topography and transmission electron microscopy (TEM) were used. Moreover, annealing of the sample at temperatures well below the growth temperature leads to the formation of striations with a period of several micrometres along the [0 1 1] direction. These striations are due to Ge-concentration fluctuations and are accompanied by the observation of D-line emission due to misfit dislocations.