ENGRI1110_Lect8_Sept14_09_posted - Photodiode (reverse bias...

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Photodiode (reverse bias p-n junction)
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Light Emitting Diodes Optoelectronic device Solid-state analog of a light bulb Draws very little current p-n junction in a forward bias Read p. 713-714, 722-730
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Light Emitting Diodes Creation of an electron-hole pair requires energy Electron-hole recombination releases energy pho to ns  (ra dia tive ) he a t pa c ke ts  o f (kine tic ) e ne rg y  lo c a lize d re g io ns  o f e nha nc e d vib ra tio ns
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Radiative Recombination cnx.org/content/m1011
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p-n junction in equilibrium (no bias)
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Why not Si? Wavelength of light emitted is not in the visible (it is  part of the Infrared, IR) Band gap of Si is 1.1 eV Si is not efficient  recombination energy can be released by non-radiative means
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Why not Si? Radiative recombination is slow because Si has an  “indirect” band gap Electrons and holes have to wait for a suitable vibration  to pass by before they can recombine radiatively  This requirement is relaxed in disordered forms of Si
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Nanocrystalline Porous Silicon Sailor Group - UCSD
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Compound Semiconductors
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Crystal Structure Diamond C, Si, Ge GaAs Zinc blende
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Band Gap Comparisons Compoun Compoun d d Eg Eg Ge 0.7 GaAs 1.4 SnSe 2.7 CuBr 2.9
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Band Gap Engineering (III-V)
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This note was uploaded on 02/10/2010 for the course ENGRI 1110 at Cornell University (Engineering School).

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ENGRI1110_Lect8_Sept14_09_posted - Photodiode (reverse bias...

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