ALLOTAXIAL GROWTH OF EPITAXIAL SI FESI2,/SI HETEROSTRUCTURES/

We fabricated Si/FeSi2/Si(111) heterostructures by a new method, calle d molecular beam allotaxy (MBA). Codeposition of silicon and iron at t emperatures around 650 degrees C leads to the formation of FeSi2 preci pitates in the crystalline silicon matrix. The subsequent annealing wa s performed in two steps. First annealing at temperatures in the range 1150-1170 degrees C resulting in the formation of high quality buried epitaxial metallic alpha-FeSi2 layers with a mininum yield value of c hi(min)=12%. Cross section transmission electron micrographs (XTEM) re veal these films to be continuous with sharp interfaces. The lowest re sistivity for alpha-FeSi2 was rho=225 mu Omega.cm at room temperature. By a second anneal at temperatures below the phase transition tempera ture the metallic alpha-FeSi2 was transformed to the semiconducting be ta-FeSi2. These first results prove the applicability of MBA for the g rowth of metallic and semiconducting FeSi2 layers in Si.