EE 121b - 3 - PN Junctions Review

EE 121b - 3 - PN Junctions Review - EE 121B Principles of...

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Slide 3-1 EE 121B – Chi On Chui EE 121B Principles of Semiconductor Device Design PN Junctions Review Professor Chi On Chui Electrical Engineering Department University of California, Los Angeles Email: chui@ee.ucla.edu
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Slide 3-2 EE 121B – Chi On Chui Outline Thermal Equilibrium Electrostatics Steady State Conditions under External Bias Reverse-Bias Breakdown Transient and AC Conditions Non-Ideal Effects (Ch. 5)
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Slide 3-3 EE 121B – Chi On Chui P N N P + + Equilibrium PN Junction “Formation” Upon joining the two materials holes ( electrons ) diffuse from the p ( n ) to n ( p ) side uncompensated acceptors N a ( donors N d + ) are left behind in the p ( n ) region near the junction A built-in E-field E is thus formed Semiconductor applet hole diff. hole drift electron diff. electron drift particle flow current Isolated, neutral p -and n -type materials PN junction
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Slide 3-4 EE 121B – Chi On Chui PN Junction Built-in (Contact) Potential The Fermi levels on both side align at equilibrium, the built-in potential is simply the difference ( E Fn –E Fp )/ q P N N P + + Isolated, neutral p -and n -type materials PN junction
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Slide 3-5 EE 121B – Chi On Chui Equilibrium Depletion (Transition Region) Width – 1 Assumptions: Abrupt doping junction Carrier depletion within W and neutrality outside W ( depletion approximation ) From Poisson’s equation P N ––– +++ +++ +++ The maximum E-field (at the metallurgical PN junction)
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Slide 3-6 EE 121B – Chi On Chui Equilibrium Depletion (Transition Region) Width – 2 The depletion width expression in terms of the contact potential (by invoking the charge balance requirement) P N ––– +++ +++ +++ V n p V 0
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Slide 3-7 EE 121B – Chi On Chui PN Junction under External Bias Equilibrium ( V = 0)
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EE 121b - 3 - PN Junctions Review - EE 121B Principles of...

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