Resonant Raman scattering from localized Si and quasiresonant Ge and Ge-Si optical phonons has been used to study the characteristics of optical transitions at energies near the E1 gap of Ge for structures of ultrathin Ge layers in bulk Si(100) and ultrathin Si layers in bulk Ge(100). Strong enhancements of the Ge-derived Raman scattering at excitation energies near 2.3 eV have been observed for Ge layers as thin as 7 AIS. Si layer scattering shows no enhancement at the Ge host resonance. These results show localized electronic states exist in these materials well above the fundamental band edges. © 1989 The American Physical Society.