Light-emitting diodes are made of Shan-Shan compounds, such as GaAs (gallium arsenide), Gap (gallium phosphide), Gaasp (gallium phosphide) and other semiconductors, the core of which is PN Junction. Therefore it has the general n knot I-N characteristic, namely is the positive guide, the reverse cutoff, the breakdown characteristic. In addition, under certain conditions, it also has luminescent properties. At the forward voltage, the electrons are injected into the P region by the N region, and the hole is injected into n by the P zone. A small number of carriers (fewer children) that enter the opposing area glow with a plurality of carriers (multiple-child), as shown in Figure 1.
If the luminescence occurs in the P region, then the injected electrons are directly compounded with the valence-band holes, or they are first captured by the center of Light and then combined with the cavity. In addition to this light-emitting compound, some electrons are captured by the center of the center (which is somewhere near the middle of the conduction belt, the intermediate band), and then again with the hole, each releasing less energy and not forming visible light. The greater the ratio of the luminous compound to the non luminous compound, the higher the optical quantum efficiency. Because the composite is luminous in the less-dispersed region, the light is produced only within μ m near the PN junction.
The theory and practice prove that the peak wavelength λ of light is related to the bandgap of semiconductor material in the luminescence region eg.
???? λ ≈ 1240-Eg (mm)
The unit of eg in the formula is electron volts (EV). If the visible light is produced (wavelength in 380nm violet Sami 80nm Red), the semiconductor material of eg should be between 3.26. The light that is longer than the red wavelength is infrared light. Infrared, red, yellow, green and blue light-emitting diodes are now available, but the cost and price of Blu-ray diode is very high.