Electronic Dielectric Constants of Crystalline and Amorphous GeSb2Te4 and Ge2Sb2Te5 Semiconductors

It is found that Phillips' spectroscopic theory of bonding for determining the zero-frequency electronic dielectric constant ε 0 can apply to crystalline and amorphous GeSb2Te4 and Ge2Sb2Te5 semiconductors. These compounds are assumed to be composed of GeTe and Sb2Te3 and have the remarkable characteristic that n 2 measured at 0.83 µm (n: refractive index) in the crystalline state is 2.2times larger than that of the amorphous state. The ε 0 values of these semiconductors in crystalline and amorphous state have been calculated from their short-range structural data. In all compounds, a good agreement with ε 0 values which correspond to n 2 at 0.83 µm has been obtained.