lecture5 - 6.720J/3.43J- Integrated Microelectronic...

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Unformatted text preview: 6.720J/3.43J- Integrated Microelectronic Devices- Spring 2007 Lecture 5-1 Lecture 5- Carrier generation and recombination (cont.) February 14, 2007 Contents: 1. G&R rates outside thermal equilibrium (cont.) 2. Dynamics of excess carriers in uniform situations 3. Surface generation and recombination Reading assignment: del Alamo, Ch. 3, 3.4-3.7 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 5-2 Key questions Outside thermal equilibrium, how is the balance between genera- tion and recombination upset for each G&R mechanism? (cont.) What governs the carriers dynamics in semiconductors outside equilibrium? In particular, if one shines light onto a semiconductor, how do the carrier concentrations evolve in time? What happens when the light is turned off? How about if the light excitation is turned on and off very quickly? How can surface G&R be characterized? 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 5-3 1. G&R rates outside equilibrium (cont.) c) Trap-assisted thermal G&R n o n>n o E c E c r o,ec =r o,ee r o,ec >r o,ee E t E t r o,hc =r o,he r o,hc >r o,he E v E v p o p>p o thermal equilibrium with excess carriers Out of equilibrium, if rate constants are not affected: r ec = c e n ( N t n t ) r ee = e e n t = c e n i n t r hc = c h pn t r he = e h ( N t n t ) = c h n i ( N t n t ) Recombination: capture of one electron + one hole net recombination rate = net electron capture rate = net hole capture rate U tr = r ec r ee = r hc r he From this, derive n t , and finally get U tr : np n o p o U tr = ho ( n + n i ) + eo ( p + n i ) 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 5-4 d) All processes combined U = U rad + U Auger + U tr 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 5-5 Special case: Low-level Injection Define excess carrier concentrations: n = n o + n p = p o + p LLI : Equilibrium minority carrier concentration overwhelmed but majority carrier concentration negligibly disturbed thermal low-level high-level equilibrium injection injection...
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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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lecture5 - 6.720J/3.43J- Integrated Microelectronic...

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