Deformation potential constants of biaxially tensile stressed Ge epitaxial films on Si(100)

The deformation potential constants at the Gamma point of Ge epitaxial films on Si(100) were determined by a combination of x-ray diffraction and photoreflectance measurements. The in-plane tensile strain in the Ge thin films was engineered by growth at different temperatures in ultrahigh vacuum chemical vapor deposition and by backside silicidation. Photoreflectance measurements and data analysis give the direct band gaps from the maxima of the light- and the heavy-hole bands to the bottom of Gamma valley, namely, E-g(Gamma)(lh) and E-g(Gamma)(hh). From the relationship between the direct band gap and the in-plane strain measured by x-ray diffraction, the dilational deformation potential of the direct band gap of Ge a, and the shear deformation potential of the valence band b were determined to be -8.97+/-0.16 eV and -1.88+/-0.12 eV, respectively. These basic constants of Ge are very important for the design of strain-engineered devices based on epitaxial Ge.