Dynamics of mid-infrared light absorption related to photoexcited charge carriers in Ge/Si quantum dots

Abstract

Mid-infrared optical absorption spectra of Ge/Si quantum dot structures in polarized light were obtained under conditions of interband optical excitation. Mid-infrared absorption changes in comparison to equilibrium conditions for certain light polarization in spectral range of 0.25 - 0.6 eV. The sign of the effect is found to be different in various spectral ranges. Transients of photoinduced absorption contain fast and slow components. The fast decay component of the absorption is related to the direct recombination of localized holes and electrons in quantum dots while a slow component is determined by significantly less probable processes of indirect in real space recombination.