The processing and characterization of CaGa2S4:Ce blue phosphor by MOCVD

— The deposition of CaS, Ga2S3, and CaGa2S4:Ce has been accomplished by MOCVD using Ca(tmhd)2, Ga(tmhd)3, and Ce(tmhd)4, with a liquid delivery system to control the flows. Samples were primarily characterized using x‐ray fluorescence and electroluminescence measurements of the color and luminance. Analysis shows the CaS deposition is mass‐transport limited, while the Ga2S3 is limited by the deposition kinetics. However, application of these mechanisms to the CaGa2S4:Ce deposition system reveals that the CaGa2S4:Ce is independent of its components. Further, the deposition of CaGa2S4:Ce is found to be Ca‐rich under conditions which lead to low Ga/Ca ratios in the deposited film. This indicates that the conversion of Ca from Ca(tmhd)2 was catalyzed by the slight presence of Ga in the form of CaGa2S4:Ce or Ga2S3 on the surface. The Ca is thought to be deposited as CaS: Ce, since there is a shift in the EL color towards green under low Ga/Ca ratios. The Ca conversion is found to approach values predicted by the CaS deposition mechanism under conditions which lead to high Ga/Ca ratios, implying that excess Ga2S3 is needed for the deposition of CaGa2S4:Ce without any CaS:Ce inclusions.