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 tha t of porous silicon. It is shown that the shape of the porous structur e is similar to that of porous silicon but with preferential etching n ear the threading dislocations. In order to investigate the influence of the porosity on the crystalline structure, high-resolution X-ray di ffraction is used to determine the strains in the layer. Moreover asym metric Bragg reflection gives the value of the lattice parameter of th e layer, parallel to the sample surface. It appears that the porosific ation has only a weak influence on the crystalline structure of the Si 1-xGex layers. (C) 1997 Elsevier Science S.A.