Lec12 PN junction I-V

# Lec12 PN junction I-V - Last Lecture: Electrostatics...

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Last Lecture: Electrostatics Summary (Equilibrium) N D -N A P N x ρ E C qV bi E i E F E V PN P A N D x N x N = ε ρ = dx d E E x ρ x = 2 ln i A D bi n N N q kT V + = D A D A bi bi N N N N q V V W 2 ) ( -x p x n -x p x n E = dx dV V x V bi -x p x n

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EECS 320 P-N Junction I-V Characteristics
Current Balanced in Equilibrium In Equilibrium, the Total current balances due to the sum of the individual components

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Band Bending Energy band diagram change with applied bias V A = 0 V A > 0 E E V E C -qV A E V E C E f E f ?
Quasi-Fermi Levels Energy band diagram change with applied bias = kT E E n n i f i exp 0 = kT E E n p f i i exp 0 = kT E E n n i fn i exp = kT E E n p fp i i exp = kT E E n n f fn exp 0 = kT E E p p fp f exp 0 a fp fn qV E E = V a < 0 (reverse bias) V a > 0 (forward bias) qV bi -qV a E V E C E fn qV a E fp qV bi -qV a E V E C E fn -qV a E fp

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Applied Bias How will the depletion region charge density, electric field, and potential change with applied bias? Sketch for zero bias, reverse bias, and forward bias ε ρ = dx d E N D -N A P N x + = D A D A bi bi N N N N q V V W 2 ) ( E = dx dV ρ
Forward Bias

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Reverse Bias
PN Junction in Forward Bias (V A >0) Current flow is proportional to e (qV A /kT) due to the exponential increase of carriers in the majority carrier bands

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## This note was uploaded on 01/31/2011 for the course EECS 320 taught by Professor Philips during the Spring '06 term at University of Michigan.

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Lec12 PN junction I-V - Last Lecture: Electrostatics...

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