Raman spectroscopy study of AgGaSe2, AgGa0.9In0.1Se2, and AgGa0.8In0.2Se2 crystals

AgGaSe2, AgGa0.9In0.1Se2, and AgGa0.8In0.2Se2 single crystals grown by the horizontal Bridgman technique were studied utilizing Raman spectroscopy excited with 633- and 784-nm lasers at temperatures varied from 77 to 300 K. The resonant Raman scattering associated with a transition from the Γ6(B) of the valence band to the conduction band Γ6 of AgGa0.9In0.1Se2crystal is demonstrated. Resonant enhancements of the longitudinal optical (LO) polar modes of Γ5 (or E) including Γ5L(W4), Γ5L(W3), Γ5L(X5), and Γ5L(Γ15), and their overtones and combinations in the crystal at 77 K were observed.