Reflectance measurements of the semiconducting compounds ${\mathrm{Mg}}_2$Si, ${\mathrm{Mg}}_2$Ge, and ${\mathrm{Mg}}_2$Sn from 0.6 to 11.0 eV at 77°K are analyzed by the Kramers-Kronig relations to yield the optical and dielectric constants. These materials crystallize in the antifluorite structure yet their optical properties are similar to those of zinc-blende semiconductors. A short discussion is included concerning the dependence of the dielectric constant upon the accuracy of the reflectance measurements and upon the choice of the arbitrary high-energy reflectance function.

• Received 21 August 1968

DOI:https://doi.org/10.1103/PhysRev.178.1353