X-RAY STUDY OF UHV-CVD FILLING OF POROUS SILICON BY GE

Using ultra high vacuum chemical vapour deposition (UHV-CVD), the pore network of porous silicon layers is filled with Ge. The evolution of the resulting structure, as a function of the Ge content, is investiga ted by X-ray diffraction. Information on the Ge crystallite size and o rientation as well as on the porous layer strains is obtained from (0 0 4) rocking curve and reciprocal space mapping measurements. The obse rvation of the ((2) over bar (2) over bar 4) asymmetric reflection all ows the determination of the relaxation state of the Ge/Si layer. The Ge growth inside the pores is epitaxial, giving a composite layer of g ood crystalline quality. After a review of the relaxation modes of the Ge deposition on Si substrates, we propose a model for the filling of porous silicon by Ge. (C) 1998 Elsevier Science B.V. All rights reser ved.