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 investigated by X-ray diffraction. Information on the Ge crystallite size and orientation as well as on the porous layer strains is obtained from (0 0 4) rocking curve and reciprocal space mapping measurements. The observation of the ((2) over bar (2) over bar 4) asymmetric reflection allows the determination of the relaxation state of the Ge/Si layer. The Ge growth inside the pores is epitaxial, giving a composite layer of good 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 reserved.