Strain-balanced Si SiGe short period superlattices: Disruption of the surface crosshatch

We have studied the effects of inserting Si/Si0.6Ge0.4 strain-balanced supe rlattices (SLs) into Si0.8Ge0.2 (001) virtual substrates. The SiGe SL layer thickness chosen was larger than the critical thickness for elastic relaxa tion and generated numerous hemicylindrical features oriented along the [10 0] directions. These features lead, when covered by Si0.8Ge0.2, to a disrup tion of the well-ordered surface crosshatch along the [110] directions, and to a significant lowering of the surface roughness. There is also evidence for some filtering of the threading dislocations by the SL. (C) 1999 Ameri can Institute of Physics. [S0021-8979(99)04314-5].