INTERSUBBAND ABSORPTION IN SI SI1-X-YGEXCY QUANTUM-WELLS/

Intersubband absorption in the valence band of Si-Si1-x-yGexCy, multiq uantum wells is reported. The quantum wells with x approximate to 17% and y approximate to 1% and thicknesses around 3 nm are grown pseudomo rphically by rapid thermal chemical vapor deposition on Si(001). The c arbon is incorporated in substitutional site using methylsilane as the gas precursor. The quantum wells exhibit near-band-edge photoluminesc ence with no-phonon and phonon-assisted replica. The energy position o f the no-phonon and phonon-assisted replica are shifted to high energy with respect to bulk alloys due to the quantum confinement of the fir st heavy hole subband. The intersubband absorption between confined su bbands is measured in a multipass waveguide geometry under optical pum ping. Absorptions for light with an electric field polarized either pa rallel or perpendicular to the growth axis are observed in both SiGe a nd SiGeC quantum wells. The absorptions peak at 100 and 130 meV and in volve bound-to-bound and bound-to-continuum transitions. The spectral positions of the intersubband absorptions are discussed from numerical calculations accounting for the band gap variation induced by carbon. (C) 1996 American Institute of Physics.