ABSTRACT
We have directly determined with pump/probe spectroscopy the light hole (LH1) excited state lifetime for the lowest heavy hole to light hole intrawell subband transitions (HH1-LH1) for 3 prototype samples of Si/SiGe strained layer superlattices, designed to have the transition energy below the optical phonon energy. We have demonstrated that the lifetime is increased by a factor of ~ 2 by bandstructure engineering of the LH1 wavefunctions for these structures. We find a decay time of 25ps for sample 1 with a well width of 5.0nm lengthens to 40ps for sample 3 with a well width of 3.0nm. In addition we have measured the lifetime for holes excited out of the well, from which we determine the lifetime for diagonal transitions (back into the well) to be ~ several hundred ps.
