Like ordinary diodes, light-emitting diodes are composed of a PN junction , and they also have unidirectional conductivity . When the forward voltage is applied to the light-emitting diode , the holes injected from the P area to the N area and the electrons injected from the N area to the P area are respectively in contact with the electrons in the N area and the voids in the P area within a few microns of the PN junction. The holes recombine and produce spontaneous emission fluorescence. The energy states of electrons and holes in different semiconductor materials are different. When electrons and holes recombine, the energy released is somewhat different. The more energy released, the shorter the wavelength of the emitted light. Commonly used are diodes that emit red, green or yellow light. The reverse breakdown voltage of the light-emitting diode is greater than 5 volts. Its forward volt-ampere characteristic curve is very steep, and a current-limiting resistor must be connected in series to control the current through the diode.
The core portion of the light emitting diode is a P-type semiconductor material and a N-type semiconductor composed of wafers , the P-type semiconductor having a transition layer and between the N-type semiconductor, known as a PN junction. In the PN junction of certain semiconductor materials, when the injected minority carriers and the majority carriers recombine, the excess energy is released in the form of light, thereby directly converting electrical energy into light energy. With reverse voltage applied to the PN junction, it is difficult to inject minority carriers, so it does not emit light. When it is in a forward working state (that is, a positive voltage is applied to both ends), when the current flows from the LED anode to the cathode, the semiconductor crystal emits light of different colors from ultraviolet to infrared, and the intensity of the light is related to the current.
The following are the inorganic semiconductor materials used in traditional light-emitting diodes and the colors they emit
LED material | Material chemical formula | colour |
Aluminum gallium arsenide gallium arsenide gallium arsenide phosphide indium gallium phosphide aluminum gallium phosphide (doped zinc oxide) | AlGaAs GaAsP AlGaInP GaP:ZnO | Red and infrared |
Aluminum gallium phosphide indium gallium nitride/gallium nitride gallium phosphide indium gallium phosphide aluminum aluminum gallium phosphide | InGaN/GaN GaP AlGaInP AlGaP | green |
Aluminum indium gallium arsenide phosphide indium gallium phosphide aluminum gallium phosphide | GaAsPAlGaInP AlGaInP GaP | High brightness orange, orange, yellow, green |
Phosphorus Gallium Arsenide | GaAsP | Red, orange, yellow |
Gallium Phosphide Zinc Indium Selenide Gallium Nitride Silicon Carbide | GaP ZnSe InGaN SiC | Red, yellow, green |
Gallium Nitride | GaN | Green, emerald green, blue |
Indium Gallium Nitride | InGaN | Near ultraviolet, blue-green, blue |
Silicon carbide (used as a substrate) | So | blue |
Silicon (used as a substrate) | Si | blue |
Sapphire (used as a substrate) | Al2O3 | blue |
Zinc selenide | ZnSe | blue |
Diamond | C | Ultraviolet rays |
Aluminum nitride, aluminum gallium nitride | AlN AlGaN | Ultraviolet rays with wavelengths from far to near |
Account not verified