The Diffusion Mechanism of Ge During Oxidation of Si/SiGe Nanofins

• Published in: ACS applied materials & interfaces Vol. 14; no. 25; pp. 29422 - 29430
• Main Authors: Thornton, Chappel S., Tuttle, Blair, Turner, Emily, Law, Mark E., Pantelides, Sokrates T., Wang, George T., Jones, Kevin S.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29.06.2022; American Chemical Society (ACS)
• Subjects: activation energy; diffusion; GAA; interfaces; layers; MATERIALS SCIENCE; mechanism; nanofins; nanowires; oxidation; SiGe; Surfaces, Interfaces, and Applications; diffusion; nanofins; SiGe; nanowires; GAA; oxidation; mechanism; Ge
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.2c05470

A recently discovered, enhanced Ge diffusion mechanism along the oxidizing interface of Si/SiGe nanostructures has enabled the formation of single-crystal Si nanowires and quantum dots embedded in a defect-free, single-crystal SiGe matrix. Here, we report oxidation studies of Si/SiGe nanofins aimed at gaining a better understanding of this novel diffusion mechanism. A superlattice of alternating Si/Si0.7Ge0.3 layers was grown and patterned into fins. After oxidation of the fins, the rate of Ge diffusion down the Si/SiO2 interface was measured through the analysis of HAADF-STEM images. The activation energy for the diffusion of Ge down the sidewall was found to be 1.1 eV, which is less than one-quarter of the activation energy previously reported for Ge diffusion in bulk Si. Through a combination of experiments and DFT calculations, we propose that the redistribution of Ge occurs by diffusion along the Si/SiO2 interface followed by a reintroduction into substitutional positions in the crystalline Si.