Crystallographic Characterization of AgGaTe₂, AgAlTe₂, and Ag(Ga,Al)Te₂ Grown by Closed-Space Sublimation

AgGaTe₂, AgAlTe₂, and Ag(Ga,Al)Te₂ layers were grown by the closed-space sublimation method on c-plane sapphire substrates. The crystallographic properties of the AgGaTe₂ and AgAlTe₂ layers were then analyzed by x-ray diffraction (XRD). Very strong 112 diffraction peaks were observed in the XRD spectra of both layers, and it was clear the (112) orientation was predominant in both layers. The orientation and domain structure of the AgAlTe₂ layer were carefully analyzed by XRD pole-figure measurement, and the effect of substrate surface atomic arrangement on the crystallinity of the AgAlTe₂ layer was investigated. On the basis of the pole-figure image, six types of {112} domain were confirmed in the layer, and [$$ \bar{1} $$1¯ 10] in one domain was regarded as aligned with the sapphire’s a-axis when the layer was formed on the c-plane sapphire substrate surface. In addition to crystallographic characterization, the optical properties of the Ag(Ga,Al)Te₂ layer were evaluated on the basis of transmittance measurements. The optical bandgap, derived from the transmittance spectrum, was approximately 2.0 eV. This value was between the bandgap values of AgGaTe₂ and AgAlTe₂. These results showed that an alloy of AgGaTe₂ and AgAlTe₂ had been grown successfully.