The wavelength range of LEDs
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The LED emits ultraviolet light to infrared light with various wavelengths. This emission wavelength is expressed by the following equation using the energy band gap (Eg) of compound semiconductor material.
λ(nm) = 1240/Eg (eV)
Larger Eg materials emit shorter wavelengths, and materials with smaller Eg emit longer wavelengths.
For infrared LEDs used in television remote controls etc., GaAs (gallium arsenide) is the material used; for red/green indicator LEDs, GaP or InGaAlP is used; and for blue LED, InGaN or GaN is used.
| Material | Energy Band gap Eg ＠300K (eV) |
Wavelength(λ） | Color |
|---|---|---|---|
| GaAs | 1.4 | 885 nm | Infrared |
| GaP | 1.8 to 2.26 | 549 to 700 nm | Green to red |
| InGaAlP | 1.9 to 2.3 | 539 to 653 nm | Green to red |
| InGaN | 2.1 to 3.2 | 388 to 590 nm | Ultraviolet to green |
| GaN | 3.4 | 365 nm | Ultraviolet to blue |
Chapter V : Optical Semiconductors
Types of Optical Semiconductors
Light-Emitting Principal of LEDs
What Is a Photocoupler?
Why Are Photocouplers Necessary?
Types of Photocouplers
Types of Photocouplers (Packages)
Types of Photocouplers (Internal Structure)
Safety Standards of Photocouplers
Characteristics of Photocouplers (Current Transfer Ratio: CTR)
Principal Characteristics of Photocouplers (Trigger LED Current)
Aging Variation Data of Photocouplers
How to Use a Photocoupler
How to Use a Photocoupler “Input Current”
How to Use a Photocoupler “Output Current”
How to Use a Photocoupler “Output-Side Resistor”
How to Use a Photocoupler Check
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