Dynamics of exciton diffusion in SiGe quantum wells on a ssV-groove patterned Si substrate

Dynamics of exciton diffusion in SiGe quantum wells (QWL’s) on a ssV-groove patterned Si substrate is investigated by using continuous-wave and time-resolved photoluminescence spectroscopy. The decay time of the luminescence arising from the (111) facet QWL’s is found to be strongly dependent on the ssV-groove period and to decrease with the increase of temperature, in contrast to the radiative lifetime of two-dimensional excitons. These behaviors are consistently explained in terms of the competition between radiative recombination and the exciton diffusion to the other regions, that is, the (100) QWL’s and the quantum wires at the bottom of the groove. By reproducing the temporal profiles of the luminescence from the (111) QWL’s, the diffusion length is deduced. The temperature dependence indicates that more efficient carrier collection from the (111) facet to the other regions can be expected at higher temperatures.