NNSE618-L20-pn-junction-current

NNSE618-L20-pn-junction-current - NNSE 618 Lecture #20 1...

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Unformatted text preview: NNSE 618 Lecture #20 1 Lecture contents P-n junction Current : Shockley model Generation-recombination current High injection NNSE 618 Lecture #20 2 First we will use Shockley approximation: Drift-diffusion current Abrupt depletion layer approximation Non-degenerate = Boltzman statistics Low injection = Fermi level do not change in the depletion layer = minority carrier densities << majority carrier densities = majority carrier density equals to doping concentration No generation/recombination in the depletion layer Let apply bias and calculate current through the p-n junction Currents in p-n junction From Sze, 1981 NNSE 618 Lecture #20 3 Currents through p-n junction: Shockley model Minority carrier current Majority carrier current Total current is constant throughout the device Recombination region Recombination region NNSE 618 Lecture #20 4 Definitions of quasi-Fermi levels: Potential across the junction: Currents in p-n junction: Shockley theory Minority carrier concentrations at the edges of the depletion region (will serve as boundary conditions): From Sze, 1981 t a V V a i p p e N n x n 2 ) ( a i V q t a V V d i n n e N n x p 2 ) ( kT E E N kT E E n n c Fn c i Fn i exp exp kT E E N kT E E n p Fp v v Fp i i exp exp Fn Fp a E E qV NNSE 618 Lecture #20 5 Lets find how minority carriers currents recombine: Continuity equation for electrons in p-region: And diffusion current (no drift in the quasi- neutral region): Combining: And similar for n-region:...
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This note was uploaded on 11/07/2011 for the course NNSE 618 taught by Professor Sergeoktyabrsky during the Spring '11 term at SUNY Albany.

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NNSE618-L20-pn-junction-current - NNSE 618 Lecture #20 1...

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