Photoluminescence and X-ray characterization of relaxed Si1-xGex alloys grown on silicon on insulator (SOI) and implanted SOI substrates

Boron and oxygen were implanted into the SiO2 region of a thin silicon on insulator (SOI) substrate to form borosilicate glass and reduce the reflow temperature needed for compliant substrates. The effect of lowering the reflow temperature was examined by characterizing a strained Si0.7Ge0.3 layer which was grown on the implanted compliant substrate by molecular beam epitaxy. Photoluminescence (PL) and triple-axis X-ray diffraction were used to characterize film quality, Ge concentration and percent relaxation, A marked decrease in the annealing temperature required (roughly a difference of 300 degrees C) to relax the Si0.7Ge0.3 layer was fully observed. The PL spectra show a broad band around 800 meV that is believed to be related to the relaxation of the SiGe layer. The intensity of this peak first increases and then decreases dramatically when the annealing temperature reaches the point when the SiGe layer begins to relax or the underlying glass begins to flow, For the sample grown on the boron and oxygen implanted BESOI, this low-energy peak is shown to disappear completely at an annealing temperature of 900 degrees C. Above 900 degrees C, we begin to see the evolution of near band-gap luminescence for the Si0.7Ge0.3 layer grown on implanted BESOI. An energy peak which shifts to higher energies, from 970 to 1025 meV, with greater relaxation is only observed for the sample grown on the implanted substrate, It is believed that the observation of near band-gap luminescence is primarily due to the reduced reflow temperature and a low-defect dislocation concentration in the Si0.7Ge0.3 film.