2. LED operating principle

The basic element of any light-emitting diode is a semiconductor with two regions of different conductivity (p- and n-type) and a region of radiative recombination of n (electrons) and p (holes) carriers. In its simplest expression, the design of an LED can be reduced to the junction of a p-doped semiconductor with the same n-doped semiconductor. This is known as a homojunction light-emitting diode. Conventional LEDs still use this structure today, but as we'll see later, the new high-intensity diodes use much more complex junctions.

Figure 2 illustrates the operating principle of a homojunction. At equilibrium, the majority carriers in each zone diffuse towards the other zone: electrons in zone n tend to diffuse towards zone...