lecture15

lecture15 - 6.720J/3.43J - Integrated Microelectronic...

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Unformatted text preview: 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 15-1 Lecture 15 - p-n Junction (cont.) March 9, 2007 Contents: 1. Ideal p-n junction out of equilibrium (cont.) 2. pn junction diode: parasitics, dynamics Reading assignment: del Alamo, Ch. 6, 6.2 (6.2.4), 6.3 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 15-2 Key questions What happens to the majority carriers in a pn junction under bias? What are the main practical issues in synthesizing pn junction diodes? How does a pn junction switch? What dominates its dynamic behavior? 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 15-3 1. Ideal p-n junction out of equilibrium (cont.) Minority carrier storage Quasi-neutrality in QNRs demands n p . Consequences: n, p x x n-x p 0 n(x) p(x) n i 2 N D n i 2 N A n(x) p(x) N A N D -Q en + Q hn -Q ep +Q hn +Q hp + Q hp Q en Q ep -w p w n compensating holes compensating electrons injected electrons injected holes In n-QNR, quasi-neutrality implies: Q hn | Q en | Q n Also, if V Q hn | Q en | with: Q hn | Q en | Q n Q hn supplied from p-contact, Q en supplied from n-contact. 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 15-4 Looks like a capacitor diffusion capacitance . Diffusion capacitance (per unit area): dQ n dQ p C d = + dV dV with: Q n = q w n p ( x ) dx x n Q p = q w x p p n ( x ) dx If both sides are long: Q n = qL h p ( x n ) = h J h ( x n ) Q p = qL e n ( x p ) = e J e ( x p ) and q q qV C d [ h J h ( x n ) + e J e ( x p )] = ( h J hs + e J es ) exp kT kT kT 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 15-5 If both sides are short and S = : 1 Q n = q p ( x n )( w n x n ) = tn J h ( x n ) 2 1 Q p = q n ( x p )( w p x p ) = tp J e ( x p ) 2 with tn and tp are the minority carrier transit times through QNRs: ( w n x n ) 2 tn = 2 D h ( w p x p ) 2 tp = 2 D e Then: q q qV C d [ tn...
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lecture15 - 6.720J/3.43J - Integrated Microelectronic...

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