Phosphorus and boron diffusion in silicon at temperatures between 900 and 1050 °C was studied both in bulk and nanostructured samples by means of scanning spreading resistance microscopy. The dopant diffusion from highly doped silicon substrates into 300–1200 nm diameter natural silicon nanopillars is clearly retarded compared to dopant diffusion in the bulk material. A three-dimensional solution of Fick’s equation enables a better understanding of dopant diffusion processes in silicon nanostructures, including all participating point defects. The observed decrease of diffusivity by 20%–50% can be explained by the injection of vacancies at the sidewalls of the pillar. The results do not provide any evidence on a possible change in point defect properties or fundamental diffusion processes in silicon nanostructures with respect to bulk silicon.

Diffusion of boron (B) in germanium (Ge) at temperatures ranging between 800 C and 900 C is revisited following the most recent results reported by Uppal et al. [J. Appl. Phys. 96, 1376 (2004)] that have been obtained mainly with implantation doped samples. In this work, we determined the intrinsic B diffusivity by employing epitaxially grown alternating undoped and B-doped Ge layer structures with three different dopant concentrations of 4 Â 10 17 cm À3 , 1 Â 10 18 cm À3 , and 3 Â 10 18 cm À3. The diffusional broadening of B was analyzed by means of secondary ion mass spectrometry (SIMS) and numerically described to determine the diffusion coefficient. Additional SIMS analyses revealed a gradient in the oxygen (O) background concentration of the epitaxially doped Ge structure. A high O content observed in near-surface regions correlates with enhanced B diffusion. In contrast, B-doped regions with low O content showed a significantly lower B diffusivity representing the intrinsic diffusivity. The B diffusion coefficients are significantly lower compared to literature data and best described by a diffusion activation enthalpy and a pre-exponential factor of (4:09 + 0:21) eV and 265 þ2256 À237 cm 2 s À1 , respectively.

Germanium (Ge) has advantageous materials properties and is considered as a mainstream material for nanoelectronic applications. Understanding dopant–defect interactions is important to form well-defined doped regions for devices. Gallium (Ga) is a key p-type dopant in Ge. In the present density functional theory study, we concentrate on the structures and electronic structures of Ga doped Ge in the presence of Ge vacancies and oxygen. We provide information on the defect structures and charge transfer between the doped Ga atom and the nearest neighbor Ge atom. The calculations show that the presence of Ga on the Ge site facilitates the formation of nearest neighbor Ge vacancies at 0.75 eV. The formation of interstitial oxygen is endoergic with the formation of −2 charge in both bulk Ge and Ga substituted Ge although the substitution of Ga has slightly less impact on the oxygen interstitial formation.