Determining Factors of LED Wavelength

LED (Light Emitting Diode) emission wavelength is primarily determined by the physical characteristics of its semiconductor materials, specifically including the following key factors:

1. Energy Band Structure of Semiconductor Materials
   The core of an LED is a semiconductor PN junction, whose emission wavelength is determined by the material's bandgap width (Eg). The narrower the bandgap width, the longer the emission wavelength (such as red light); the wider the bandgap width, the shorter the wavelength (such as blue light).
    For example: Gallium Nitride (GaN) has a larger bandgap width, emitting blue light (~450nm); Indium Gallium Phosphide (InGaP) has a smaller bandgap width, emitting red light (~620nm).
2. Doping and Material Composition
   By adjusting the proportion of doping elements in semiconductors (such as Indium (In) content in InGaN), the emission wavelength can be precisely controlled.
   For example: Increasing In content in InGaN causes the wavelength to shift from blue light toward green light.
3. Quantum Well Structure
   Quantum wells further regulate energy levels and emission wavelength by restricting the movement of electrons and holes, commonly used in high-precision wavelength design.
4. Temperature Effects
   Temperature increase causes the semiconductor bandgap width to decrease, resulting in wavelength red-shift (for example, blue LED may shift toward green at high temperatures).
5. Operating Voltage and Current
   Forward voltage is directly related to wavelength: the shorter the wavelength (such as ultraviolet light), the higher the required voltage (typically above 3V); the longer the wavelength (such as infrared light), the lower the voltage (approximately 1.3V).
6. Phosphor (White Light LED)
   White light LEDs typically use blue light chips to excite phosphor (such as YAG phosphor), and the phosphor composition affects the final color temperature.

Other Considerations

Power Independence: LED wavelength is determined by the material and is unrelated to power (the wavelength of a 10W LED still depends on the chip material).
Wavelength Range Limitations: Conventional LED wavelengths range from 380-780nm (visible light); infrared LEDs above 1100nm require special materials (such as Gallium Arsenide).

Typical Materials and Wavelength Correspondence Table