Near-band-gap photoluminescence of Si1−xGex alloys grown on Si(100) by molecular beam epitaxy

Publisher Website
Google Scholar
Abstract
Photoluminescence spectra in the near‐band‐gap region of Si1−xGex alloys (x=0.04 and 0.15) grown on Si(100) substrates by molecular beam epitaxy have been measured at 4.2 and 12 K. Radiative recombinations of free and bound excitons in thin layers of Si1−xGex alloys have been clearly observed for the first time. No‐phonon transitions and transverse‐optical (TO) phonon‐assisted transitions have been identified.The luminescence lines become broader with an increase in excitation intensity; the broadening is interpreted to be due to the generation of the bound multiexciton complexes (BMECs). The position of the band‐edge luminescence lines is determined by the strain in the epitaxial layer as well as the alloy composition. The defect‐related L band appears in the case of x=0.15.