Deformation potential constants of biaxially tensile stressedGeepitaxial films onSi(100)

Abstract

The deformation potential constants at the $\Gamma$ point of $\mathrm{Ge}$ epitaxial films on $\mathrm{Si}\left(100\right)$ were determined by a combination of x-ray diffraction and photoreflectance measurements. The in-plane tensile strain in the $\mathrm{Ge}$ 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, $E_g^{\Gamma }\left(lh\right)$ and $E_g^{\Gamma }\left(hh\right)$. 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 $\mathrm{Ge}$ $a$, and the shear deformation potential of the valence band $b$ were determined to be $-8.97\pm 0.16\mathrm{eV}$ and $-1.88\pm 0.12\mathrm{eV}$, respectively. These basic constants of $\mathrm{Ge}$ are very important for the design of strain-engineered devices based on epitaxial $\mathrm{Ge}$.