Chapter 4 Lecture - Part 1

Excitation and recombination result in emission of

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Unformatted text preview: es Common – LED’s • Current used to inject electrons into semiconducting Current crystal. • Excitation and recombination result in emission of Excitation photons with energy related to bandgap. photons • Higher bandgap results in shorter wavelength – Phosphors • Excitation by way of a-c field. Recombination Mechanisms Recombination • Direct recombination Direct – is constant in time (spontaneous) is – Recombination lifetimes: Recombination • • Statistical description of this rate Two key cases: – Excess electrons in p-type material – Excess holes in n-type material • In each case, the recombination lifetime is expressed in In terms of the majority carrier concentration. terms – Bottom line: In direct recombination, majority carrier Bottom concentrations decay at the same rate as minority carrier concentrations. carrier Recombination Mechanisms Recombination • Indirect recombination (trapping) Indirect – More common than direct recombination in Si More – Involves interaction with recombination levels that Involves lie within the bandgap lie • These levels are associated with lattice defects and These impurities in the SC impurities • Recombination centers must be able to receive one type of Recombination carrier and then be able to capture the other type in order to facilitate e-h annihilation. to • It’s a two st...
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This note was uploaded on 04/02/2014 for the course EECS 321 taught by Professor Zorman during the Spring '10 term at Case Western.

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