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Browse Prior Art Database

Pillbox Quantum Well Light-Emitting Diode

IP.com Disclosure Number: IPCOM000100904D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

VanZeghbroeck, BJ: AUTHOR

Abstract

An efficient high-power light-emitting diode (LED) structure is described. The device lends itself for use in short multimode fiber links because of the short coherence length and broad spectrum.

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Pillbox Quantum Well Light-Emitting Diode

       An efficient high-power light-emitting diode (LED)
structure is described.  The device lends itself for use in short
multimode fiber links because of the short coherence length and broad
spectrum.

      The circular device is shown schematically in the drawing.  The
LED consists of a small pillbox-like structure with a separate
confinement single quantum well vertical layer structure.  To obtain
optimum efficiency, the diameter must be smaller than the absorption
length which, for a single quantum well with a 3% confinement factor,
is about 30 mm.  The diode should also be larger than the diffusion
length of the carriers in the material, which is about 3.5 mm.  A
diameter d of 10 to 20 mm is thus appropriate.  A 45-degree angled
mirror reflects the light in the direction perpendicular to the
surface.  Because of the small size, the emitted light can easily be
coupled into a multimode fiber which may have a diameter of 50 mm.

      High efficiency is obtained since the light can escape the
crystal over a larger solid angle than would be the case for a planar
surface emitting LED.  This higher efficiency also yields higher
maximum output power.  Since merely the optical coupling across the
GaAs- Air interface is improved, the increased output power can be
obtained at the same current and without modulation bandwidth
reduction.