Can Si be used to make LEDs ?
Si can be used as a substrate in LEDs, but it cannot be used in the p-n junction because the bandgap energy is too small to produce visible light.
Technically: Yes. But it has an indirect bandgap, so you really wouldn't want to.
The energy bandgap of Si at room temperature is 1.12eV. Since the relationship between photon energy and wavelength is E(eV)=1.24/wavelength(micrometers), one can calculate that Si could emit a ligth in infrared optical spectrum: wavelength=1.24/1.12eV=1.11 micrometers. BUT, Si is indirect semiconductor! And therefore does not emit significant amounts of light due to the requirement of momentum conservation in optical transitions.
Oct 30, 2011