DISLOCATION-RELATED PHOTOLUMINESCENCE IN SI1-XGEX/SI(100) GROWN BY MOLECULAR-BEAM EPITAXY

Photoluminescence (PL) in Si1-xGe(x) alloys grown on Si(100) by molecular beam epitaxy (MBE) has been studied over the composition range 0 less-than-or-equal-to x less-than-or-equal-to 0.5. For x greater-than-or-equal-to 0.15, strong deep-level luminescence has been observed. Sharp lines which are similar to the dislocation-related D-lines in Si appear in the spectra for x = 0.15 and 0.26. Transmission electron microscopy (TEM) for these samples reveals that there are a lot of dislocations at the Si1-xGe(x)/Si interface and in the Si substrate. The dislocations in the Si substrate are considered to be the origin of the sharp luminescence lines. These PL lines for x = 0.15 cannot be observed in the case of thin layers. In that case, the density of the dislocations near the interface is much lower. For x = 0.38 and 0.50, broad bands appear in the spectra. The TEM observations in these cases reveal that there are many dislocations in the Si1-xGe(x) layers and that the dislocation density in the Si substrate is very low. The broad bands are considered to originate from the dislocations in the Si1-xGe(x) layer.