Physics Question #1512

Furqan, a 21 year old male from Lahore asks on July 22, 2003,

Why don't ordinary Silicon diodes emit light like LED's?

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The answer

Barry Shell answered on July 22, 2003

It has to do with the band gap. This is the energy required for the semiconductor material (eg: silicon with some impurities) to jump from being an insulator to a conductor. In an ordinary solid state diode, this gap is at energies that result in heat. In an LED, the energy is released as light. It's more complicated than this, but that is the basic reason. You can find out more at ChipCenter.

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