Creating An Internal Electric Field

Regions of p-type boron-doped silicon and n-type phosphorous-doped silicon are created adjacent to one another. Some free electrons in the n-type region cross over and fall into the holes in the p-type region where they remain permanently. As this cross over process continues, every boron site that contributed a hole becomes permanently negatively charged, and every phosphorous site that gave up an electron becomes permanently positively charge.

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