Photoluminescence studies of isotopically enriched silicon: isotopic effects on the indirect electronic band gap and phonon energies

We have performed high-resolution photoluminescence spectroscopy on silicon crystals with different isotopic composition and investigated the effects of this composition on the indirect electronic band gap and phonon energies. From the relative energy shift of the indirect electronic band gap between two crystals of different isotopic composition, the zero-point renormalization energy of that electronic band gap was estimated. The experimentally determined phonon frequency shifts between crystals of different isotopic composition are compared with theoretically predicted frequency shifts. We further present a detailed analysis of the different contributions leading to the observed phonon frequency shifts.