10 Radiative Recombination

10 Radiative Recombination - Radiative...

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adiative Recombination Radiative Recombination EE 47410
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Radiative Recombination mi d t li ht mitti d i s Semiconductor light emitting devices rely on recombination of electrons and holes in the product of the recombination is the emission of a E c photon. Radiative recombination events E v conserve energy and momentum. Thus direct band gap materials are preferred materials in which to build ght emitting devices because E light emitting devices because conservation of momentum occurs without the involvement of a momentum conserving entity such as a k phonon. The inverse of radiative recombination is absorption of a photon by the generation of an lectron- ole pair E h electron hole pa r , eh e photon e h EE k k hk k  
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E c E E v k Because momentum is easily conserved in a direct bandgap material, absorption processes (generation) are stronger in these materials, as well. At equilibrium, recombination and generation are in balance and the rates at which electrons and holes are generated equals the rate at which they recombine, esulting in a steady state equilibrium concentrations of electrons and holes resulting in a steady state equilibrium concentrations of electrons and holes, n o and p o . For undoped , intrinsic material n o = p o = n i . However, it is also true that the product n o p o = n i 2 for intrinsic and extrinsic material alike.
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This note was uploaded on 02/23/2011 for the course EE 474 taught by Professor Lingo during the Spring '11 term at USC.

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10 Radiative Recombination - Radiative...

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