why are led heavily doped?
Answers
The accelerated deployment of light-emitting diode (LED) bulbs is on track to save U.S. consumers and businesses $20 billion a year in electricity costs within a decade, which would lower U.S. CO2 emissions by some 100 million metric tons a year! The growing global effort to speed up LED adoption could ultimately cut global energy costs and carbon pollution 5 times as much.
because led's working principle is recombination. when Electrons and holes recombine, they release the energy/photons whose frequency lies in the visible spectrum (we need visible light, right). So in order to get that particular frequency, we need a material whose energy gap will be of same energy. so electron will absorb the electrical energy (just enough to cross the gap) and then jump into conduction band. And after very very very small time it will fall back into the hole and release that energy in the form of photon (with the frequency between visible region). So we need a material whose energy gap will be same as the energy of visible photons. And it turns out that we don't have that material. But we can make it artificially by mixing Gp 13 and 15 elements together. So leds do not contain Gp14 elements (Si, Ge), but contains only Gp13 and 15. For ex : Gallium Arsenide, Gallium Phosphide. Mainly led contains Indium gallium nitride. So you can see that semiconductors used in making led do not have impurities of gp13 or 15. actually it is made up of gp13 and 15 mixture (which were considered as impurities). So we can say that it's heavily doped.