Question 5.3: Find an expression for the electron current in the n-type ma...

Solid State Electronic Devices

Find an expression for the electron current in the n-type material of a forward-biased p-n junction.

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The total current is

I=qA\left(\frac{D_{p} }{L_{p} }P_{n}+\frac{D_{n} }{L_{n} }n_{p} \right)(e^{qV/kT}-1 )

The hole current on the n side is

I_{p} (x_{n} )=qA\frac{D_{p} }{L_{p} } P_{n} e^{-x_{n}/L_{p} } (e^{qV/kT}-1 )

Thus the electron current in the n material is

I_{n} (x_{n} )=I-I_{p} (x_{n} )=qA\left[\frac{D_{p} }{L_{p} } (1-e^{-x_{n}/L_{p} } )P_{n}+\frac{D_{n} }{L_{n} } n_{p} \right](e^{qV/kT} -1)

This expression includes the supplying of electrons for recombination with the injected holes, and the injection of electrons across the junction into the p side.

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