Suppression of Surface Roughening on Strained Si/SiGe Layers by Lowering Surface Stress

Stress-induced surface roughening usually occurs in strained semiconductor layers, such as SiGe layers on Si substrates, which is technologically undesirable. We demonstrate that the roughening of a strained Si0.34Ge0.66 layer is suppressed by depositing a thin Si layer (≤1.5 nm). This thin Si layer is not stressed on the SiGe layer, which is lattice-matched to the Si substrate. The thin Si layer lowers the surface stress of the strained heterostructure, thereby preventing the surface roughening. The main advantage of this method is that the surface roughening can be suppressed by making only a minor change in crystal growth procedure.