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Questions

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Questions

Complete the following diagrams and expressions. Some questions may have more information than

necessary.

1. In a Si pn junction, with the p-type to the left, draw a plot of the net charge p(x) as a function

of location. Assume that the junction is symmetric, meaning NA = ND and all impurities are

ionized. The depletion region width is W, and the max {E (x) } is Emax

(Junction Center)

(NA)

Emax

(Spartial coordinate within the pn juction)

(Decrease in Net charge density)

(ND)

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2. Draw a plot of an electric field E(x). Find an expression of 2Ɛ Emax / W

(Junction center)

(Depeltion area)

Emax (P-side)

(Spartial coordinate within the pn junction)

Emax (N-side)

(Depletion area)

In this case the electric field in the depletion region of a pn junction can be expressed as

E(x) = Emax * (1 -2x/ W)

Where

. E (x) is the electric field at position x

. Emax is the maximum electric field magnitude

. X is the spatial coordinate within the pn junction

. W is the width of the depletion region

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3. Draw a plot of the potential V(x), assuming the p-type os grounded show Vbi in the plot

(Junction center)

(potential has returned to ground level)

(OV)

(p-type) region

(n-type) region

(Vbi)

(Potential has returned to ground)

This V(x) plot shows a transition in how the potential p-type moves to the n-regions, therefore

showing how potential decreases linearly from Vbi on the …

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