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

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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: Jesús 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: Jesús 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 υ > Eg Eg h υ 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: Jesús 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: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007....
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lecture4 - 6.720J/3.43J Integrated Microelectronic Devices...

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