Electronic transitions in a SimGen strained monolayer superlattice measured by photoreflectance

The first photoreflectance spectrum from a short-period strain-symmetrized SimGen superlattice has been measured at 87 K. Fifteen electronic transitions were measured between 1.1 and 2.7 eV and fit well to a third derivative functional form. Most of the transition energies were calculated using a one-band envelope-function model, adding strain and spin orbit shifts as first-order corrections. Additional transitions were observed near the expected interband energies in an unstrained Si0.2Ge0.8 random alloy. All of the calculated transition energies were found to agree to within 80 meV of the measured values.