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Polycrystalline Luminescent Thin Film

IP.com Disclosure Number: IPCOM000082714D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

DiStefano, TH: AUTHOR

Abstract

Polycrystalline thin films have a low-luminous efficiency, because recombination at the Brain boundary quenches luminescence. Doping the Brain boundary enhances the luminous efficiency by keeping minority carriers away from the region of the grain boundary.

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Polycrystalline Luminescent Thin Film

Polycrystalline thin films have a low-luminous efficiency, because recombination at the Brain boundary quenches luminescence. Doping the Brain boundary enhances the luminous efficiency by keeping minority carriers away from the region of the grain boundary.

Polycrystalline thin films have not been especially useful as DC luminescent materials because of their low-conversion efficiency, which is due partly to the nonluminescent recombination of electrons at the grain boundaries. Electrons injected into the material will diffuse a considerable distance before recombination (e.g., about 10-100 mu for GaAs over a range of concentrations of p-doping). Since grain size is typically less than 10 mu, an injected electron has a high probability of recombination at a grain boundary.

This problem can be circumvented to some extent by selective doping of the grain boundary. The doping profile is such that thermal electrons are repelled away from the boundary, as illustrated schematically in Figs. 1 and 2.

For the undoped material in Fig. 1, electrons collect in the grain boundaries where they recombine. The grain boundaries are doped to produce p/+/ material so that each p-type grain has a thin coating of p/+/ material, as in Fig. 2a, e.g., by zinc diffusion into p-type polycrystalline GaAs. At low temperatures, the dopant diffuses primarily into the grain boundaries and not into the grains.

After the dopant is in the boundaries, it is d...