3.2 - 3.2 PN Junction I-V Characteristic 3.2.1 Qualitative...

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ECE3080, Chapter 3.2 1 May 30, 2005 ECE 3080: Chapter 3.2 – PN Junction O. Brand, 1 of 18 3.2 PN Junction: I-V Characteristic 3.2.1 Qualitative Derivation 3.2.2 Quantitative Derivation – Minority Carrier Distribution – Minority Carrier Currents – I-V Characteristic – Saturation Current Pierret, Chapter 6, page 235-259 May 30, 2005 ECE 3080: Chapter 3.2 – PN Junction O. Brand, 2 of 18 3.2.1 Qualitative Derivation (a) Equilibrium Under equilibrium, the net current flow is zero , i.e. the electron/hole drift and diffusion currents balance each other Electron Currents: – Majority carrier diffusion current from n- to p-side – Minority carrier drift current from p- to n-side Hole Currents: – Majority carrier diffusion current from p- to n-side – Minority carrier drift current from n- to p-side J = J drift + J diff = 0 Pierret, Fig. 6.1
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ECE3080, Chapter 3.2 2 May 30, 2005 ECE 3080: Chapter 3.2 – PN Junction O. Brand, 3 of 18 Qualitative Derivation (b) Forward Bias Forward bias (V A > 0) reduces the potential drop across the depletion region As a result, the majority carrier (electron and hole) diffusion over the potential hill increases exponentially, resulting in a net current flow across the junction The minority carrier drift currents remain constant Pierret, Fig. 6.1 Majority carrier density decreases exponentially with increasing energy E n(E) p(E) May 30, 2005 ECE 3080: Chapter 3.2 – PN Junction O. Brand, 4 of 18 Qualitative Derivation (c) Reverse Bias Reverse bias (V A < 0) increases the potential drop across the depletion region As a result, the majority carrier (electron and hole) diffusion current over the potential hill is suppressed for –V A > few kT The minority carrier drift currents remain constant, thus resulting in a saturation current flowing in reverse direction Pierret, Fig. 6.1
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ECE3080, Chapter 3.2
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3.2 - 3.2 PN Junction I-V Characteristic 3.2.1 Qualitative...

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