LEDs can be divided into many different types and divided into different colors. So, what is the difference between different LEDs? What kind of LEDs do we usually see on the basis of what? What advantages do they have in comparison? The secret of purple and blue LEDs is revealed for you today.
Purple LED
A diode that emits ultraviolet light. Generally speaking, an LED having an emission center wavelength of 400 nm or less is sometimes referred to as a near-ultraviolet LED when the emission wavelength is greater than 380 nm, and is referred to as a deep ultraviolet LED when it is shorter than 300 nm. Due to the high sterilization effect of short-wavelength light, UV LEDs are often used for sterilization and deodorization of refrigerators and home appliances...
A diode that emits ultraviolet light. Generally speaking, an LED having an emission center wavelength of 400 nm or less is sometimes referred to as a near-ultraviolet LED when the emission wavelength is greater than 380 nm, and is referred to as a deep ultraviolet LED when it is shorter than 300 nm. Since the short-wavelength light has a high sterilization effect, the ultraviolet LED is often used for sterilization and deodorization of refrigerators and home appliances, and LEDs that emit visible light in combination with a phosphor. For example, a red, green, and blue phosphor is combined with an ultraviolet LED to obtain a white LED.
Ultraviolet LEDs mainly use GaN-based semiconductors. In terms of products , Nichia Chemical Industry has listed a variety of luminescent center wavelengths ranging from 365nm to 385nm, and Nitride Semiconductor has marketed a variety of luminescent center wavelengths ranging from 355nm to 375nm.
The development of deep ultraviolet LEDs with wavelengths below 300 nm is also active. In 2008, the Institute of Physics and Chemistry and Matsushita Electric Industrial Co., Ltd. announced that a deep-ultraviolet LED with an illuminating center wavelength of 282 nm and an optical output power of 10 mW was developed using InAlGaN of GaN-based semiconductors. For deeper wavelength LEDs with shorter wavelengths, the NTT Institute of Physical Science and Basics developed a deep-UV LED with an emission center wavelength of 210 nm using AlN materials.
A diode that emits infrared light. Generally refers to LEDs with an emission center wavelength exceeding 700 nm. It is mostly used as a light source for remote controllers and infrared communication, a distance measuring sensor light source, a photocoupler light source, and a light source for a printer head. The infrared LED uses a GaAs-based semiconductor material such as AlGaAsP.
Blue LED
Refers to the blue LED. The center of the emission wavelength is around 470 nm. A light source for a blue display portion such as a lighting fixture and an indicator, a blue light source for an LED display panel, and a backlight source of the liquid crystal panel. Use in combination with a phosphor material to obtain white light. Current white LEDs generally use a combination of blue LEDs and fluorescent materials.
The opportunity for the wide application of blue LEDs was the first time in 1993 that Nichia Chemical Industry developed a variety of light intensity of more than 1 cd. Prior to this, there were no LEDs with high blue purity and practical light intensity. Therefore, a large-size display using LEDs cannot achieve full-color display.
The material of the blue LED uses a gallium nitride (GaN)-based semiconductor. In the past, blue LEDs were developed using zinc selenide (ZnSe) semiconductors. However, since the development of high-brightness blue LEDs using GaN-based semiconductors in December 1993, the mainstream of blue LEDs has become GaN-based. Semiconductor products.
The blue LED is configured such that an aluminum nitride (AlN) semiconductor layer and a GaN-based semiconductor layer are stacked on a surface of a sapphire or SiC substrate or the like. A structure in which a p-type GaN-based semiconductor layer and an n-type GaN-based semiconductor layer are overlapped is provided in a portion called an active layer and blue-emitting light.
The pn junction is the structure that must be used to make high-brightness LEDs. Among LEDs such as red, which use materials other than GaN, the pn junction is a mainstream structure long ago. Before the introduction of high-brightness blue LEDs in 1993, it was difficult to achieve pn junctions using GaN-based materials. The reason is that the formation of the n-type GaN-based semiconductor layer is relatively simple, but the fabrication of the p-type GaN-based semiconductor layer is difficult. After that, by using a multiple quantum well structure for the GaN-based semiconductor layer disposed between the p-type GaN-based semiconductor layer and the n-type GaN-based semiconductor layer, and further improving the quality of the GaN-based semiconductor layer, the light intensity is greatly improved.
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