Blue Phosphors for Full-Color High-Definition Video Display

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Thin-film electroluminescent technology now produces matrix-addressed self-luminous flat panels which come very close to providing the capability for high-definition color television. The principal obstacle to advancing this technology to full-color video imaging is the need for high-brightness, saturated-blue phosphor. The most promising available candidate is ZnS:Tm, which has excellent chromaticity but luminance that is too low by 1-2 orders of magnitude. Its weak emission is inconsistent with its intense blue cathodoluminescence and photoluminescence and is due, most likely, to defects. We will maximize the luminance of ZnS:Tm-type phosphors as a function of film structure; optimal charge compensation by specific anions and co-activation by other lanthanides will also be assessed. Thin phosphor films will be grown by conventional metalorganic chemical vapor deposition after a 10-30 nm seed layer is formed by atomic layer epitaxy in the same large-area reactor. The resultant establishment of a uniform large- diameter columnar grain structure is expected to greatly increase electroluminance. Further, this deposition process is capable of laying down all of the primary ZnS-host phosphors for full-color display in a single chamber, it is amenable to lower-cost non- photolithographic pixel definition, and it is inherently scalable.