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lecture2 - 6.720J/3.43J Integrated Microelectronic Devices...

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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 2-1 Lecture 2 - Carrier Statistics in Equilibrium February 8, 2007 Contents: 1. Conduction and valence bands, bandgap, holes 2. Intrinsic semiconductor 3. Extrinsic semiconductor 4. Conduction and valence band density of states Reading assignment: del Alamo, Ch. 2, §§ 2.1-2.4 (2.4.1) Announcement: Go to http://ilab.mit.edu and register. Select member­ ship in the 6.720 group. You will need this to access the lab for the Device Characterization Projects. 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].
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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 2-2 Key questions What are these ”energy band diagrams”? What are these ”holes”? In a perfectly pure semiconductor, how many electrons and holes are there? Can one engineer the electron and hole concentrations in a semi­ conductor? 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].
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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 2-3 1. Conduction and valence bands, bandgap, holes energy E c conduction band valence band E c bandgap E g E v E v space coordinate Conduction and valence bands: bonding electrons occupy states in valence band ”free” electrons occupy states in conduction band holes : empty states in valence band CB electrons and VB holes can move around: ”carriers” + + - - a) a) b) c) b) c) 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].
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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 2-4 electron energy hole energy hole energy E c E v - - - - + + + + Elements of energy band diagrams: at edges of bands, kinetic energy of carriers is zero electron energies increase upwards hole energies increase downwards electron energy h υ = Eg h υ > υ > Eg Eg - - + + - + h υ > Eg a) b) E c E v 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].
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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 2-5 2. Intrinsic semiconductor Define intrinsic semiconductor , or ”ideal” semiconductor: perfectly crystalline (no perturbations to periodic lattice) perfectly pure (no foreign atoms)± no surface effects± Question: How many electrons and holes are there in an intrinsic
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