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-FeSi 2 on Si(1 1 1) substrates by molecular beam epitaxy (MBE). By the optimization of growth temperature ( T s ) and Si/Fe flux ratio, the β-Fe(Si 1− x Ge x ) 2 with a flat surface was grown at T s =500 °C and Si/Fe=0.5, which were different from the optimized condition of the undoped β-FeSi 2 ( T s =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 ( E g ) measured by photoreflectance measurements, the E g decreased with the increase of Ge concentration. These results revealed that β-Fe(Si 1− x Ge x ) 2 was successfully grown on Si(1 1 1) substrate in the range of x =0−11%.