Allotaxial growth of epitaxial Si/FeSi 2/Si heterostructures

Abstract

We fabricated Si/FeSi 2/Si(111) heterostructures by a new method, called molecular beam allotaxy (MBA). Codeposition of silicon and iron at temperatures around 650°C leads to the formation of FeSi 2 precipitates in the crystalline silicon matrix. The subsequent annealing was performed in two steps. First annealing at temperatures in the range 1150–1170°C resulting in the formation of high quality buried epitaxial metallic α-FeSi 2 layers with a minimum yield value of X min = 12%. Cross section transmission electron micrographs (XTEM) reveal these films to be continuous with sharp interfaces. The lowest resistivity for α-FeSi 2 was ϱ = 225 μΩ·cm at room temperature. By a second anneal at temperatures below the phase transition temperature the metallic α-FeSi 2 was transformed to the semiconducting β-FeSi 2. These first results prove the applicability of MBA for the growth of metallic and semiconducting FeSi 2 layers in Si.