Effect of Substrate Biasing on the Epitaxial Growth and Structural Properties of RF Magnetron Sputtered Germanium Buffer Layer on Silicon

High-quality single-crystal-like Ge (004) thin films have been epitaxially grown using radio-frequency magnetron sputtering on Si (001) substrates successfully. The crystalline quality of the Ge films can be obviously improved by applying a positive bias on the substrate holder. X-ray diffraction measurements show that the single-crystal-like Ge film has a narrow full width at half maximum of 0.26 degrees. The perpendicular lattice constant (a(Ge)(perpendicular to)) and in-plane lattice constant (a(Ge)(parallel to)) are 0.5671 and 0.564 nm. The Raman shift full width at half maximum shows that the defects in the film are obviously reduced. Transmission electron microscopy diffraction patterns also show that the Ge (004) film has good crystalline quality. The results can be applied as Ge buffer layers on Si substrates for the fabrication of high-efficiency III-V solar cells and photodetectors.