Metal-organic chemical vapor deposition of the blue electro-luminescent cerium-doped calcium thiogallate from a liquid reagent delivery system

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:207473

Moss, T S; Dye, R C; Smith, D C; Samuels, J A ^[1]; DelaRosa, M J; Schaus, C F ^[2]

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1. Los Alamos National Lab., NM (United States)
2. Planar Systems, Inc., Beaverton, OR (United States)

Deposition of CaS, Ga{sub 2}S{sub 3}, and CaGa{sub 2}S{sub 4}:Ce has been accomplished by MOCVD using Ca(tmhd){sub 2}, Ga(tmhd){sub 3}, and Ce(tmhd){sub 4}, with bubblers and with a liquid delivery system to control the flows. Samples were primarily characterized using x-ray fluorescence and electroluminescence measurements of the color and brightness. Deposition using the bubblers showed a definitive relationship between the Ga(tmhd){sub 3} bubbler temperature and the Ga XRF counts. The Ca conversion shows a tenuous relationship with the Ca(tmhd){sub 2} bubbler temperature, but the scatter of the data makes determining a correlation impractical. Use of the liquid delivery system is preferred to the bubblers because it delivered a reliable reagent flow without the same problems of degradation of the reagent over time. Analysis shows the CaS deposition is mass transport limited, while the Ga{sub 2}S{sub 3} is limited by the deposition kinetics. However, application of these mechanisms to the CaGa{sub 2}S{sub 4}:Ce deposition system reveals that the CaGa{sub 2}S{sub 4}: Ce is independent of its components. Further, the deposition of CaGa{sub 2}S{sub 4}:Ce is found to be Ca rich under conditions which leads to lew Ga/Ca radios in the deposited film. This indicates that the conversion of Ca from Ca(tmhd){sub 2} was catalyzed by the slight presence of Ga in the form of CaGa{sub 2}S{sub 4}:Ce or Ga{sub 2}S{sub 3} 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 also found to approach values predicted by the CaS deposition mechanism under conditions which lead to high Ga/Ca ratios, implying that excess Ga{sub 2}S{sub 3} is needed for the deposition of CaGa{sub 2}S{sub 4}:Ce without any CaS:Ce inclusions.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: Department of Defense, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 207473
• Report Number(s): LA-UR--95-4500; CONF-951155--51; ON: DE96007302
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM SULFIDES
CERIUM ADDITIONS
CHEMICAL VAPOR DEPOSITION
DISPLAY DEVICES
ELECTROLUMINESCENCE
GALLIUM SULFIDES
PHOSPHORS