Semiconductor emitter junctions

Light-emitting semiconductor devices use electroluminescence as a physical effect. The phenomenon of electroluminescence is attributed to the radiative recombination of excess charge carriers injected into the vicinity of, say, a P-N junction.

The energy released in the form of radiation is equal to the difference between the energy of the ionized state, known as the "electron-hole pair", and the energy of the bound state (recombined electron and hole).

Two conditions must be met for light emission to occur. Firstly, the probability of a radiative transition must be high, and secondly, there must be a high density of carriers capable of making this transition.

The first point is obtained...