Lecture7

Lecture7 - ECE ECE 124A VLSI Principles Lecture 7...

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CE 124A ECE 124A LSI Principles VLSI Principles Lecture 7 pn pn-junction Diode, MOS Capacitor and MOS junction Diode, MOS Capacitor and MOS-FET FET Prof. Kaustav Banerjee Electrical and Computer Engineering ail: [email protected] ucsb edu E-mail: [email protected] Lecture 7, ECE 124A, VLSI Principles Kaustav Banerjee
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Semiconductor Physics Tutorial: Key Points to Remember… ond Model Bond Model Nearest neighbor atoms covalently bonded with valence electrons (=4 for Si) At absolute zero temperature….no free electrons As temp. increases, thermal energy (kT) causes ome of the covalent electrons to break loose to some of the covalent electrons to break loose….to become conduction electrons. .( intrinsic ) Absence of an electron causes a “void” or a “hole” Dopantswith an extra (one less) electron contribute toward increasing the number of conduction electrons (holes): n-type and p-type (extrinsic) Lecture 7, ECE 124A, VLSI Principles Kaustav Banerjee semiconductors
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Semiconductor Physics Tutorial: ey Points to Remember Key Points to Remember… Band Model When many atoms are brought together….discrete energy levels are replaced with bands of energy states separated by gaps…due to Pauli Exclusion Principle At absolute zero, most of the lower energy bands are completely filled….and upper energy bands are completely empty….thus no conduction…like a full or empty bottle of water! alence band due to the valence electrons (mostly bound) Valence band : due to the valence electrons (mostly bound) Conduction band : due to the conduction electrons Top edge of valence band---E V ottom edge of conduction band - Bottom edge of conduction band---E C Band gap: E G = E V –E C (=1.1 eV in Si) how to measure E G ? Energy band diagrams are drawn w.r.t electrons…. onor (acceptor) energy levels are drawn close to the Lecture 7, ECE 124A, VLSI Principles Kaustav Banerjee Donor (acceptor) energy levels are drawn close to the conduction (valence) band edges…. why?
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Semiconductor Physics Tutorial: ey ey oints to Remember… oints to Remember… Key Key Points to Remember… Points to Remember… Band Model Effective mass concept…. Acceleration = F/m = -qE/m e (for electrons); = qE/m h (for holes) A more complete description of the electrons in a crystal is based on their wave characteristics Electron wave function ( ) is a solution to the 3-dimensional Schrodinger’s equation: H = E Solution is of the form: = exp (± k.r ); where k is the wave vector 2 the electron wavelength) = 2 π / λ ( λ is the electron wavelength) k is a function of energy, E Effective mass of electrons/holes are related to the curvature of e E- curves why? the E k curves…. .why? Density of states: D(E) = number of states/ Δ E x Volume Effective density of states in valence (N v ) and conduction (N c ) ands… Lecture 7, ECE 124A, VLSI Principles Kaustav Banerjee bands… Thermal equilibrium and Fermi function---- Fermi-Dirac distribution function: 1/(1 + exp (E-E F )/kT)
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This note was uploaded on 12/04/2010 for the course ECE 134 taught by Professor York during the Fall '08 term at UCSB.

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Lecture7 - ECE ECE 124A VLSI Principles Lecture 7...

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