Pulsed laser annealing for high-efficiency thin film electroluminescent devices

Thin film electroluminescent (TFEL) structures composed of ZnS:Mn (phosphor ) and Y2O3 (insulator) films were annealed using pulsed (similar to 20 ns) KrF laser irradiations under an environment of 150 psi (similar to 10.34 ba rs) of argon. The crystallinity of both layers was studied via x-ray diffra ction analysis. Their degree of lattice misfit and the integrated diffracti on line intensities were examined to assess the thermal effects of pulsed l aser annealing. In agreement with a thermal model of the laser-matter inter action and previous results, we suggest that the pulsed laser annealing tec hnique improves the luminescent efficiencies of thin film electroluminescen t phosphors by generating an in-depth solid-state phase transition. We repo rt that the laser processed TFEL structure exhibits better display performa nce than equivalent devices thermally annealed at a temperature of 450 degr ees C as demonstrated by sharper turn-on response and also an increase in b rightness by a factor greater than four times. We attribute these performan ce improvements to a smaller lattice misfit value, which has been previousl y correlated to interface states density. (C) 2000 American Institute of Ph ysics. [S0021-8979(00)04115-3].