X-ray diffraction and electron microscopy investigation of porous Si1-xGex

A structural study of p- and p(+)-type porous Si1-xGex materials and a comparison with non-porous epitaxial Si1-xGex layers is reported. The pore morphology is studied by electron microscopy and compared to that of porous silicon. It is shown that the shape of the porous structure is similar to that of porous silicon but with preferential etching near the threading dislocations. In order to investigate the influence of the porosity on the crystalline structure, high-resolution X-ray diffraction is used to determine the strains in the layer. Moreover asymmetric Bragg reflection gives the value of the lattice parameter of the layer, parallel to the sample surface. It appears that the porosification has only a weak influence on the crystalline structure of the Si1-xGex layers. (C) 1997 Elsevier Science S.A.