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We report the determination of the diffusion coefficient of Si in crystalline Ge over the temperature range of 550 to 900 °C. A molecular beam epitaxy (MBE) grown buried Si layer in an epitaxial Ge layer on a crystalline Ge substrate was used as the source for the diffusion experiments. For samples annealed at temperatures above 700 °C, a 50 nm thick SiO 2 cap layer was deposited to prevent decomposition of the Ge surface. We found the temperature dependence of the diffusion coefficient to be described by a single activation energy (3.32 eV) and pre-factor (38 cm 2 /s) over the entire temperature range studied. The diffusion of the isovalent Si in Ge is slower than Ge self-diffusion over the full temperature range and reveals an activation enthalpy which is higher than that of selfdiffusion. This points to a reduced interaction potential between the Si atom and the 2 native defect mediating the diffusion process. For Si, which is smaller in size than the Ge self-atom, a reduced interaction is expected for a Si-vacancy (Si-V Ge ) pair. Therefore we conclude that Si diffuses in Ge via the vacancy mechanism.

We present experimental results of dopant-and self-diffusion in extrinsic silicon doped with As. Multilayers of isotopically controlled 28 Si and natural silicon enable simultaneous analysis of 30 Si diffusion into the 28 Si enriched layers and dopant diffusion throughout the multilayer structure. In order to suppress transient enhanced self-and dopant diffusion caused by ion implantation, we adopted a special approach to dopant introduction. First, an amorphous 250-nm thick Si layer was deposited on top of the Si isotope heterostructure. Then the dopant ions were implanted to a depth such that all the radiation damage resided inside this amorphous cap layer. These samples were annealed for various times and temperatures to study the impact of As diffusion and doping on Si self-diffusion. The Si self-diffusion coefficient and the dopant diffusivity for various extrinsic n-type conditions were determined over a wide temperature range. We observed increased diffusivities that we attribute to the increase in the concentration of the native defect promoting the diffusion.