It was proposed that a compliant substrate which consisted of a thin epitaxial Si film on a high-density porous layer plus a low-density porous layer should be used to grow high-quality hetero-epitaxial layers. Films of SiGe, which were above the critical thickness, were grown onto such substrates by means of molecular beam epitaxy. Transmission electron microscopy showed that the Si0.8Ge0.2 films contained no dislocations due to elastic strain relaxation alone. On the other hand, plastic flow in pseudomorphic films that were grown on conventional Si substrates occurred and generated dislocations.

GeSi Films with Reduced Dislocation Density Grown by Molecular-Beam Epitaxy on Compliant Substrates Based on Porous Silicon S.I.Romanov, V.I.Mashanov, L.V.Sokolov, A.Gutakovskii, O.P.Pchelyakov: Applied Physics Letters, 1999, 75[26], 4118-20