Like semiconductor lasers, semiconductor light emitting diodes are also PN junctions, which emit light by injecting electrons into the PN junction from an external power source. The semiconductor light emitting diode, as LED, is composed of P layer formed by P-type semiconductor, N layer formed by N-type semiconductor, and active layer formed by double heterostructure in the middle. The active layer is a luminous area with a thickness of 0.1 ～ 0.2 μ M or so.

LED

Semiconductor light emitting diodes are widely used in photoelectric systems because of their simple structure, small volume, small working current, convenient use and low cost.

Under forward bias, semiconductor PN junction or its similar structure can emit visible light or near-infrared light. This device that directly converts electrical energy into light energy is called light emitting diode, or LED for short.

Luminescence is a process in which the energy stored in an object in some way is converted into light radiation. The light radiation of a luminous object is generated when the excited electrons in the material transition to the ground state. Semiconductors (mainly compound semiconductors composed of Group III and Group V elements in the periodic table of elements) are current excited electroluminescent devices.

The phenomenon of electroluminescence was discovered in 1923 and did not attract people's attention at that time. With the development of modern technology, new requirements are put forward for light-emitting devices. It is hoped that light-emitting tubes are simple, reliable, long life, low price and miniaturization. Therefore, the research on electroluminescence has been very active since the 1960s.