University of California, BerkeleyEE230 - Solid State ElectronicsProf. J. BokorRecombination Handout.fmRecombination Processes(reading in supplementary references: Singh, Pankove)Radiative recombinationRadiative recombination is the reverse of absorption. If excess carriers are present, the sys-tem is not in equilibrium. This can lead to the emission of photons which is sometimesreferred to as luminescence.Luminescence is sometimes specified based on the method of excitation as follows:We can calculate the emission rate and spectrum from absorption rate and spectrum. Themethod is similar to the Einstein A & B coefficient analysis for atoms.We put the system in thermal equilibrium. Then emission rate = absorption rate. The ther-modynamic principle of detailedbalanceholds that the rates must balance for eachfre-quency ν.We also can relate the absorption probability to the absorption coefficient:Excitation ProcessEmission ProcessCurrent InjectionElectroluminescenceOptical Excitation PhotoluminescenceElectron Beam ExcitationCathodoluminescenceUltrasonic Acoustic ExcitationSonoluminescenceRν()dνPν()ρ ν()dν=emissionrate per unitvolumeprobabilityper unit timeof absorbingphoton νdensity of pho-tons of freq ν
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