Chapter 4 Lecture - Part 1

To capture processes at a recombination level a hole

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Unformatted text preview: ep process with two energy transitions • Energy loss due to recombination generally does not lead Energy to the production of photons but rather heat. to Capture processes at a recombination level (a) hole capture at a filled recombination center; (b) electron capture at an empty center. Recombination Mechanisms Recombination • Indirect recombination (trapping) Indirect – Net effect: the annihilation of an e-h pair with no net Net change in the electron concentration in the recombination center recombination – Carrier lifetimes • Complicated to calculate due to unequal times to capture Complicated each carrier each • Can be extended if the first carrier is reexcited thermally Can before capture of the second carrier. before – Temporary trapping: situation when a carrier is Temporary trapped and then is reexcited without annihilation. • The recombination center is, in this case, called a trap. Recombination Mechanisms Recombination • Indirect recombination (trapping) Indirect – Deep traps: Deep • Lies deep in the gap, midgap or greater • These traps are generally slow in releasing trapped carriers These because much energy is required for reexcitation. because – Impurities in Si • • • See Figure...
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