lecture4 - 6.720J/3.43J- Integrated Microelectronic...

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Unformatted text preview: 6.720J/3.43J- Integrated Microelectronic Devices- Spring 2007 Lecture 4-1 Lecture 4- Carrier generation and recombination February 12, 2007 Contents: 1. G&R mechanisms 2. Thermal equilibrium: principle of detailed balance 3. G&R rates in thermal equilibrium 4. G&R rates outside thermal equilibrium Reading assignment: del Alamo, Ch 3. 3.1-3.4 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 4-2 Key questions What are the physical mechanisms that result in the generation and recombination of electrons and holes? Which one of these are most relevant for Si at around tempera ture? What are the key dependencies of the most important mecha nisms? If there are several simultaneous but independent mechanisms for generation and recombination, how exactly does one define thermal equilibrium? What happens to the balance between generation and recombi nation when carrier concentrations are perturbed from thermal equilibrium values? 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 4-3 1. Generation and recombination mechanisms a) Band-to-band G&R , by means of: phonons (thermal G&R) photons (optical G&R) E c h > Eg Eg h E v heat heat thermal thermal optical radiative generation recombination absorption recombination thermal G&R: very unlikely in Si, need too many phonons si multaneously (about 20) optical G&R: unlikely in Si, indirect bandgap material, need a phonon to conserve momentum 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]. b) 6.720J/3.43J- Integrated Microelectronic Devices- Spring 2007 Lecture 4-4 Auger generation and recombination , involving a third carrier E c E v hot-electron hot-electron hot-hole hot-hole assisted assisted assisted assisted Auger Auger Auger Auger generation recombination generation recombination Auger generation: energy provided by hot carrier Auger recombination: energy given to third carrier; needs lots of carriers; important only in heavily-doped semiconductors Cite as: Jess del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007....
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lecture4 - 6.720J/3.43J- Integrated Microelectronic...

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