Studies of boron diffusivity in strained Si1-xGex epitaxial layers

Diffusion of boron in compressively strained Si1-xGex alloy layers grown by rapid pressure chemical vapor deposition has been studied as a function of Ge fractions for 0.0006 less than or equal tox less than or equal to0.15 a nd annealing temperature. The comparison of the Si1-xGex samples to the Si samples after rapid thermal and furnace anneals revealed a retarded B diffu sion inside the strained Si1-xGex epitaxial layers. The influence of the Ge content on the dopant diffusion was also measured and simulated, demonstra ting that the diffusion of B and the extracted bang-gap change was found to decrease with the Ge alloy content, and the extracted activation energies for diffusion were found to increase with increasing Ge content in the inve stigated composition range. The influence of various factors on the B diffu sivity is studied and their importance is discussed elaborately. A simple e mpirical expression for the B retardation is presented and incorporated int o a diffusion model for dopants in heterostructures. Good agreement between the measured and simulated diffusivity that includes the model for strain and chemical effects is obtained. (C) 2001 American Institute of Physics.