Optical Spectra of Some II-IV-V2Ternary Compounds

Abstract

The polarized-reflectance spectra between 2.0 and 5.2 eV and the logarithmic derivative of the reflectance at 2 K for the ternary compounds ZnSi${\mathrm{As}}_2$, CdSi${\mathrm{As}}_2$, CdSn${\mathrm{As}}_2$, and CdSn${\mathrm{P}}_2$ are reported. All the structure observed in previous electroreflectance data is seen in the logarithmic-derivative spectra plus some additional weak structure. The $E_1$ reflectance structures consist of three or more peaks; it is suggested that the additional splitting of the $E_1$ transitions is due to a separation in energy of the $\Lambda$ and $L$ critical points. No evidence is found in the optical spectra for the presence of ${\Gamma }_{15}^v$ to $X_1^c$ or $X_3^c$ "pseudo-direct" transitions. The chalcopyrite crystalline structure, how it relates to zinc blende, its effect on the band structure, and group theory as applied to the chalcopyrites are discussed in detail.