Why LEDs use gallium arsenide and not any of the semiconductors like silicon?

Question

Why LEDs use gallium arsenide and not any of the semiconductors like silicon?

Answer 1

Silicon cannot produce visible light as electricity apply to it.

Answer 2

LEDs are made from a variety of semiconductors depending on the color you want to get.

http://www.oksolar.com/led/led_color_cha...

Answer 3

When sufficient energy is applied to a semiconductor (through heat, vibration, applied voltage, etc.) to force electrons from their valence band across the forbidden band and above the Fermi energy level, up into the conduction band, those electrons are in an excited state.  When these exited electrons drop back to the valence band, they release a photon of equivalent energy to the gap energy.

In Silicon, the energy gap is the same energy as an infared photon.  Silicon photodiodes and solid-state lasers are excellent for use in fiberoptic communications in the infared band.

In order to produce visible photons, you need materials that have higher energy gaps.  These are created when you alloy metals like Gallium and Arsenic.  By adding the right amounts of Aluminum, Gallium, Phosphorous, Arsenic, and Indium, the energy gap (from valence to conduction) can be taylored to produce colors ranging from deep red to green.

(Note: blue, violet, ultraviolet, and white LEDs have even higher energy gaps and require even different materials).

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