Growth condition dependence of Ge-doped β-FeSi2 epitaxial film by molecular beam epitaxy

Abstract

We have investigated the growth condition of Ge-doped β-FeSi2 on Si(111) substrates by molecular beam epitaxy (MBE). By the optimization of growth temperature (Ts) and Si/Fe flux ratio, the β-Fe(Si1−xGex)2 with a flat surface was grown at Ts=500°C and Si/Fe=0.5, which were different from the optimized condition of the undoped β-FeSi2 (Ts=670°C, Si/Fe=2.0). In the dependence of lattice constants on Ge concentration, all the lattice constants expanded in the range of x=0–11%. In the direct transition energies (Eg) measured by photoreflectance measurements, the Eg decreased with the increase of Ge concentration. These results revealed that β-Fe(Si1−xGex)2 was successfully grown on Si(111) substrate in the range of x=0−11%.