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Pure-Ge/Si short period superlattice (SPS) grown by gas source MBE (GSMBE) is studied by photoluminescence spectroscopy and Raman scattering spectroscopy. An abnormal band in photoluminescence is found in an intermediate range of Lsi between 1.9 nm-2.9 nm for samples with LGe fixed at 1.5 ml. In contrast to a pure-Ge/Si quantum well, the energy of the band shows red-shift as Lsi increases. Raman scattering shows that Si-Si vibration related Raman shift reaches a minimum for samples with strongest PL intensity of the abnormal band. It is therefore concluded that the abnormal band is related with strain relaxation process.
Pure-Ge / Si short period superlattice (SPS) grown by gas source MBE (GSMBE) is studied by photoluminescence spectroscopy and Raman scattering spectroscopy. An abnormal band in photoluminescence was found in an intermediate range of Lsi between 1.9 nm-2.9 nm for samples with contrast of a pure-Ge / Si quantum well, the energy of the band shows red-shift as Lsi increases. Raman scattering shows that Si-Si vibration related Raman shift reaches a minimum for samples with strongest PL intensity of the abnormal band. It is therefore concluded that the abnormal band is related with strain relaxation process.