3.1 PN Junction Electrostatics

3.1 PN Junction Electrostatics - Chapter 3 The PN Junction...

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ECE3080, Chapter 3.1 1 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 1 of 24 Chapter 3 – The PN Junction 3.1 PN-Junction Electrostatics 3.2 I-V Characteristic 3.3 Non-Idealities 3.4 Dynamic Behavior Literature: Anderson, Chapter 5-6, page 239-345 Anderson, Supplement 2, page 346-371 Pierret, Chapter 5-8, page 195-343 Sze, Chapter 4, page 84-127 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 2 of 24 The PN Junction I = I s e qV A /kT ! 1 " # $ % I-V Characteristic P N Circuit Symbol + Forward Bias Reverse Bias +
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ECE3080, Chapter 3.1 2 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 3 of 24 3.1 PN Junction: Electrostatics 3.1.1 PN Junction Basics – Junction Approximations – Band Structure – Built-In Potential 3.1.2 Step PN Junction – Equilibrium V A = 0 – External Bias V A 0 3.1.3 Linearly Graded PN Junction – Equilibrium V A = 0 – External Bias V A 0 Anderson, Chapter 5.1-5.3.2, page 239-263 Pierret, Chapter 5, page 195-226 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 4 of 24 3.1.1 PN Junction Basics Example: Diffusion of donor atoms (e.g. P) in p-substrate Metallurgical junction at N A = N D or N D – N A =0 Net Doping N D – N A Anderson, Fig. 5.1
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ECE3080, Chapter 3.1 3 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 5 of 24 Doping Profile Approximations for PN Junctions Approximations for doping profile in pn junctions: Step Junction : approximation for ion implantation or shallow diffusion into lightly doped wafer Linearly Graded Junction : approximation for deep diffusion in moderately to heavy doped wafer Step Junction Linearly Graded Junction Pierret, Fig. 5.2 May 30, 2007 ECE 3080: Chapter 3.1 – PN Junction O. Brand, 6 of 24 PN Junction Band Diagram Equilibrium requires the Fermi level to be constant across the device Regions far away from the metallurgical junction will be unaffected Electrons diffuse from n- to p- side, holes from p- to n-side, leaving behind unbalanced dopant site charges This space charge creates an electric field (band bending), resulting in a carrier drift balancing the carrier diffusion ( J tot = 0 ) Anderson, Fig. 5.2 Electron Affinity: χ = E vac - E C Workfunction: Φ = E vac - E F Ionization Potential: γ = E vac - E V
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ECE3080, Chapter 3.1
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This note was uploaded on 08/25/2010 for the course ECE 3080 taught by Professor Staff during the Spring '08 term at Georgia Tech.

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3.1 PN Junction Electrostatics - Chapter 3 The PN Junction...

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