A diode is a simple semiconductor device. It contains a junction with N-type and P-type silicon. The positively charged P-type silicon has boron serving as a dopant. The N-type silicon sits on the other side of the junction with a negative charge. The junction exists to stop the flow of electrical current: it prevents the flow of electrons in one direction, while allowing electricity in the other. In a semiconductor device the flow of electrons occurs when a voltage is present in the correct polarity.

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