Synthesis and characterization of rare earth doped ternary chalcogenide semiconductors: effective electro-luminescence and laser materials

Thiogallate compounds represented by general formula MGa2S4 [where M- Ca+2, Ba+2, Sr+2, Pb+2, Eu+2, Eu+3, (Na+1La+3) and (Na+1Ce+3)] are highly effective electro-luminescence and laser materials. These materials were first synthesized in 1971 and studied by many groups due to their possible applicability in opto-, and quantum- electronics. Forbidden band gap (ΔE) at room temperature (RT) for these materials varies in a wide range from ΔE ∼ eV for CaGa2S4 to ∼ 2.32 eV for Ca4Ga2S7. In the present paper the results of structural properties and photoluminescence (PL) measurements (temperature range of 77 – 300 K) of melt grown Ca4Ga2S7 single crystals doped with 5 at% of rare earth (RE) Eu2+ (Ca4Ga2S7 : Eu2+) are described for the first time. It is shown that, broadband PL with a maximum at 660 nm is caused with intra shell transitions 4f65d - 4f7(8S7/2) of Eu2+ ions.