We have used e-beam lithography and reactive ion etching (RIE) to pattern (
100) Si substrates prior to overgrowth with SiGe alloys by molecular beam e
pitaxy (MBE). The structuring process was designed to give lines with well
defined width and orientation as well as a defect free Si crystal surface.
Using atomic force microscopy, it was shown that the relaxation of SiGe buf
fer layers strongly depends on the width and the orientation of the mesa li
nes. A significant reduction in the dislocation density compared to the unp
atterned areas of the samples can be obtained. The photoluminescence spectr
a of the SiGe buffers and Si quantum wells (QWs) grown on top of buffer lay
ers confirm the non-isotropic relaxation process in the line shaped mesas.
This method reveals novel possibilities for the manufacture of Si-based ele
ctronic devices.