The symmetries and splittings of the uppermost valence bands in orthorhombic and chalcopyrite AgIn${\mathrm{S}}_2$ have been determined from electroreflectance measurements on oriented crystals using polarized radiation. The principal features of the valence-band structures in both phases are dominated by the deviations of the lattice constants from ideal wurtzite and chalcopyrite, respectively. On the other hand, the small splitting of the lowest two valence bands in orthorhombic AgIn${\mathrm{S}}_2$ is attributed to the "wurtzite-like" potential. The lowest band gaps at 300 °K in the orthorhombic and chalcopyrite phases are 1.98 and 1.86 eV, respectively.

• Received 1 October 1973

DOI:https://doi.org/10.1103/PhysRevB.9.1719