Lecture10(2)

Wavelength optical absorption vs wavelength optical

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Unformatted text preview: ical Absorption vs. Wavelength EE 332 Spring 2013 Photogeneration Photogeneration •  Each Photon with energy greater than Eg can result in one electron-hole-pair. Thus, we can say, •  If α is small (near bandgap), the generation profile can be approximately constant. If α is large (hν>>Eg), the generation profile can be approximately as at the surface. •  EE 332 Spring 2013 Re-define Mass Action Law (1) Excess Carrier Generation GThermal r np r ni2 RThermal Mass action law is not valid: G > R Non-equilibrium state Re-define Mass Action Lawoptical Illumination: (2) Under GThermal GLight r np Under optical Illumination: n p n no n p po p Re-define Mass Action Law (2) GThermal GLight r ( po n)(no n) GThermal GLight r ( o Re-no n) Mass Action p n n)( define Under optical Illumination: p GLight G r noG o r(pno n)(n Under rn 2 p po n) optical Illumination: n n p Thermal Thermal Light E o CE 440: r o Mohamed Mohamed Since: GThermal G GTHERMAL p no p n n2 r n o p G G n Thermal Light ro o r Law o o Light r ( po n)(no n) r GTHERMAL GThermal GLight r no po r no po n r n GLight r no po n rno2po Since: GLight ECEr440: o po n rn 2 n Since: Mohamed Mohamed GTHERMAL r no po EE 332 Spring 2013 Low-Level Injection Low-Level Injection Case ) (Special Low-level Injection: Excess EHP is much smaller than the majority carrier (n0 p0 ) n GLight r no po n rn Using: 2 negligible 1 r no po GLight Under low-level excitation: ECE 440: Mohamed Mohamed n n EE 332 Spring 2013 Mi...
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This document was uploaded on 02/18/2014.

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