Solid State Electronic Devices, 7th Edition

8.2 Light-​Emitting Diodes

When carriers are injected across a forward-​biased junction, the current is usually accounted for by recombination in the transition region and in the neutral regions near the junction. In a semiconductor with an indirect band gap, such as Si or Ge, the recombination releases heat to the lattice. On the other hand, in a material characterized by direct recombination, considerable light may be given off from the junction under forward bias. This effect, called injection electroluminescence (Section 4.2.2), provides an important application of diodes as generators of light. The use of LEDs in digital displays is well known. There are also other important applications, in traffic and automotive signals and in illumination. ...