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lecture10 - 6.720J/3.43J Integrated Microelectronic Devices...

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Unformatted text preview: 6.720J/3.43J Integrated Microelectronic Devices - Spring 2007 Lecture 10-1 Lecture 10 - Carrier Flow (cont.) February 28, 2007 Contents: 1. Minority-carrier type situations Reading assignment: del Alamo, Ch. 5, 5.6 Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J Integrated Microelectronic Devices - Spring 2007 Lecture 10-2 Key questions What characterizes minority-carrier type situations? What is the length scale for minority-carrier type situations? What do majority carriers do in minority-carrier type situations? Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J Integrated Microelectronic Devices - Spring 2007 Lecture 10-3 Overview of simplified carrier ow formulations General drift-diffusion situation (Shockley's equations) 1D approx. Quasi-neutral situation (negligible volume charge) Majority-carrier type situation (V=0, n'=p'=0) Space-charge situation (field independent of n, p) Minority-carrier type situation (V=0, n'=p'=0, LLI) Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J Integrated Microelectronic Devices - Spring 2007 Lecture 10-4 Simplified set of Shockley equations for 1D quasi-neutral situations p n + N D N A 0 J e = qnv drift + qD e n e x J h = qpv drift qD h p h x 1 p = J h n t = J e 1 q G ext U + G ext U or x t q x J t x 0 J t = J e + J h Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J Integrated Microelectronic Devices - Spring 2007 Lecture 10-5 1. Minority-carrier type situations Situations characterized by: excess carriers over TE no external electric field applied (but small internal field gener- ated by carrier injection: E = E o + E ) Example: electron transport through base of npn BJT. Two approximations: 1. E small | v drift | |E| 2. Low-level injection for n-type: n n o p p U p negligible minority carrier drift due to E (but cant say the same about majority carriers) Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007....
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This note was uploaded on 09/24/2010 for the course EECS 6.720J taught by Professor Jesúsdelalamo during the Spring '07 term at MIT.

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lecture10 - 6.720J/3.43J Integrated Microelectronic Devices...

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