Dopant Diffusion in Si1-xGex Thin Films: Effect of Epitaxial Stress

Alain Portavoce; Isabelle Berbezier; Antoine Ronda; Patrick Gas; J.S. Christensen; Andrej Yu. Kuznetsov; Bengt Gunnar Svensson

doi:10.4028/www.scientific.net/DDF.249.135

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Dopant Diffusion in Si_1-xGe_x Thin Films: Effect of Epitaxial Stress
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HomeDefect and Diffusion ForumDefect and Diffusion Forum Vol. 249Dopant Diffusion in Si1-xGex Thin Films: Effect of...

Dopant Diffusion in Si_1-xGe_x Thin Films: Effect of Epitaxial Stress

Abstract:

We have investigated the lattice diffusion of B and Sb by means of molecular beam epitaxy in Si1−xGex (x < 0.2) layers grown on Si(001) substrate. Using Si1−xGex relaxed buffers we were able to differentiate the chemical effect (change in the Ge composition) as opposite to the biaxial stress effect (due to the epitaxy on Si) on dopant diffusion. B diffusion follows a behavior opposite to Sb diffusion versus Ge composition and biaxial stress. These results are explained in view of the difference of diffusion mechanism between B (interstitials) and Sb (vacancies). We also show that dopant diffusion follows contrasting behaviors under biaxial pressure and hydrostatic pressure, and that the activation volume of dopant diffusion is of opposite sign for biaxial pressure and for hydrostatic pressure. This is explained using a formalism based on the extra work done by the system for diffusion under pressure, concluding that for biaxial stress the activation volume depends mainly on the relaxation volume linked to the defect formation.