Lecture15(1)

57 e 0029 a cm 2 055 a cm 2 ee 332 spring 2013 review

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Unformatted text preview: Lp J p = 0.57 × e −0.029 A / cm 2 = 0.55 A / cm 2 EE 332 Spring 2013 Review of Excess Carriers •  •  •  •  Equilibrium and non-equilibirum carriers Generation and recombination (τr) Steady state carrier generation – Quasi-Fermi Levels Diffusion Ø།  Diffusion vs. drift processes (Dn, Dp) Ø།  Build-in fields Ø།  Continuity equation Ø།  Diffusion and recombination (Lp) 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 RHow Does n and p Change with Light? ecombination Constant light illumination: n no n p po p Shining a light creates an equal number of Excess Electron-hole pair Light is turned off at t=0: Recombination Dynamics t n(t ) no ne -t/τn t 0 n p(t ) po pe t n n p ECE 440: Mohamed Mohamed EE 332 Spring 2013 light on energy band: Fermi Levels ed with 5x1014 donors and 4x1014 a...
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