PHOTOLUMINESCENCE AND RAMAN-SPECTRA OF SI SI1-XGEX STRAINED SUPERLATTICES UNDER HIGH-PRESSURE/

We investigated photoluminescence spectra in strained Si/Si1-xGex supe rlattices as a function of pressure. The double-crystal X-ray diffract ion patterns prove that there is tetragonal lattice distortion in the alloy layer grown epitaxially on a Si substrate. The effects of lattic e distortion and alloy composition are confirmed by Raman spectra. The excitonic photoluminescence spectra are assigned to the free-excitoni c no-phonon transitions and their phonon replicas. The photoluminescen ce peaks show negative pressure dependencies of -15.0 to -16.0 meV/GPa . This result means that the conduction-band minimum is at the X point as in bulk Si.