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

摘要

Thiogallate compounds represented by general formula MGa_2S_4 [where M- Ca~(+2), Ba~(+2), Sr~(+2), Pb~(+2), Eu~(+2), Eu~(+3), (Na~(+1)La~(+3)) and (Na~(+1)Ce~(+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 (?E) at room temperature (RT) for these materials varies in a wide range from ?E ~ 4 eV for CaGa_2S_4 to ~ 2.32 eV for Ca_4Ga_2S_7. In the present paper the results of structural properties and photoluminescence (PL) measurements (temperature range of 77 - 300 K) of melt grown Ca_4Ga_2S_7 poly-crystals doped with 5 at% of rare earth (RE) Eu~(2+) (Ca_4Ga_2S_7: Eu~(2+)) are described for the first time. It is shown that, broadband PL with a maximum at 660 nm is caused with intra shell transitions 4f~65d - 4f~7(~8S_(7/2)) of Eu~(2+) ions.