High efficiency planar MCLEDs

Joray, Reto; Stanley, R. P.; Ilegems, M.

doi:10.1002/pssb.200560969

Cited by 2 publications

(1 citation statement)

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“…This led to develop mirrors of increasingly high reflectivity, resulting in a longer photon lifetime at small in-plane momenta, inside the planar structure (see e.g. the contributions by Oesterle et al [105] and by Joray et al [70] to the present volume). It was thanks to these advances that the exciton-photon coupling rate became faster than the damping, and the first strong-coupling sample was produced.…”

Section: Introductionmentioning

confidence: 87%

Fifteen Years of Microcavity Polaritons

Savona

2006

The Physics of Semiconductor Microcavities

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In semiconductors with a direct interband optical transition, the fundamental electronic excitations above the ground state are excitons, namely hydrogen-like bound electron-hole pairs. In a perfect bulk semiconductor material, however, a correct description of the excited states must include the linear coupling of excitons to the electromagnetic field. This coupling gives rise to normal modes that are linear superpositions of one exciton and one photon mode, called exciton-polaritons . Exciton-polaritons are the actual excited states of a bulk semiconductor.Bulk polaritons were suggested in 1958 by J. Hopfield [58] and measured a few years later by means of non-linear optical spectroscopy [2,52,57,152]. The normal-mode coupling for polaritons is aresult of momentum conservation in the exciton-photon interaction. This selection rule imposes a one-to-one coupling between exciton and photon modes having the same momentum. As a consequence, within the linear coupling regime, the situation is analogous to that of two linearlycoupled harmonic oscillators. Two normal modes at different energies, the upper and the lower polariton, are formed. Due to the very different exciton and photon energy dispersion, as a function of momentum, polariton modes display an anticrossing with a minimum energy separation that can be as large as 16 meV in bulk GaAs [2]. Within the anticrossing region, polaritons are full admixtures of exciton and photon modes, while they have pure exciton or photon character far from it.The concept of polaritons remained linked to the physics of bulk semiconductors for more than two decades. The progress in fabrication of epitaxial semiconductor heterostructures, particularly quantum wells (QWs) led naturally to a description of their electronic excitations in terms of the polariton concept. However, because of the mismatch in the dimensionality of excitons (2D) and photons (3D), momentum conservation applies only to the in-plane component, and one exciton mode couples to a continuum of photon modes, resulting in an irreversible radiative decay instead of a normal-mode coupling [6,44]. Only at larger in-plane momenta, photon modes that are evanescent in the direction orthogonal to the QW can form surface polari- Physics of Semiconductor Microcavities: From Fundamentals toNanoscale DevicesEdited by Benoit Deveaud

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Section: Introductionmentioning

confidence: 87%