Optical properties of the ${\mathrm{Cd}}_3$${\mathrm{As}}_2$-${\mathrm{Cd}}_3$${\mathrm{P}}_2$ semiconductor alloy system

The near-normal-incidence, room-temperature reflectance spectra of the ${\mathrm{Cd}}_3$ ${\mathrm{As}}_2$-${\mathrm{Cd}}_3$ ${\mathrm{P}}_2$ semiconductor alloy system have been measured for photon energies $0.083<E<\mathrm{}21\mathrm{}$ eV. Synchrotron radiation has been used to extend the measurements to 30 eV for ${\mathrm{Cd}}_3$ ${\mathrm{As}}_2$. These spectra are similar to those of III-V compounds. Comparison of the primary, reflectance data with the results of others and with the band-structure calculations has been made. The reflectance has been analyzed via the Kramers-Kronig relations. We report curves for $n$, $k$, ${\kappa }_1$, ${\kappa }_2$, and $n_{\mathrm{eff}}$ for all the alloys studied. Strong structure in the fundamental absorption scales approximately linearly with alloy composition. Structure at 11 eV is associated with Cd $d$-band excitation.