Bandgap Energy and refractive index

In summary, the conversation discusses the relationship between bandgap energy (Eg) and refractive index (n) of a material. The equations presented (Eq1 and Eq2) do not directly relate Eg to n, leading to confusion about the logic behind the statement that higher Eg results in higher n. A paper was found that demonstrates the complexity of this relationship.
  • #1
Martel_lu
1
0
The statement that the higher the bandgap energy Eg, the lower the refractive index of material is confusing me.

If I start from two equations.
Eq1: Eg=hc/lamda_g
Eq2: lamda=lamda_0/n

Higher Eg means lower lamda_g. It means in order to have the light in semiconductor material with wavelength of lamda_g, we have to increase n.
That comes out the conclusion that higher Eg, Higher n.

I don't know where is the logic wrong.
 
  • #3
Neither equation relates the band gap to the refractive index. So, the logic ypu are seeking cannot be found from these equations alone.
A quick google search resulted in finding this paper that shows how complicated this relationship is: https://web.njit.edu/~sirenko/PapersNJIT/Ravi_IPT_2007.pdf.
 

Related to Bandgap Energy and refractive index

1. What is bandgap energy?

Bandgap energy refers to the minimum energy required for an electron to move from the valence band to the conduction band in a semiconductor material. It is also known as the energy gap and is measured in electron volts (eV).

2. How does bandgap energy affect the properties of a material?

The bandgap energy determines whether a material is a conductor, semiconductor, or insulator. Materials with smaller bandgap energies are better conductors, while those with larger bandgap energies are insulators. The bandgap energy also affects the color of a material, as it determines which wavelengths of light will be absorbed or emitted.

3. What is the relationship between bandgap energy and refractive index?

The refractive index of a material is inversely proportional to its bandgap energy. This means that materials with higher bandgap energies will have lower refractive indices, while materials with lower bandgap energies will have higher refractive indices. This relationship is important in understanding the optical properties of materials.

4. How is the bandgap energy of a material determined?

The bandgap energy of a material can be determined through various methods, such as optical spectroscopy, electrical measurements, and theoretical calculations. The most common method is through optical spectroscopy, where the absorption or emission of light is measured at different wavelengths to determine the bandgap energy.

5. Can the bandgap energy of a material be changed?

Yes, the bandgap energy of a material can be changed through various methods, such as doping, alloying, and strain engineering. Doping involves introducing impurities into the material to alter its electronic properties, while alloying involves combining different materials to create a new material with a different bandgap energy. Strain engineering involves applying mechanical stress to a material to change its electronic properties and thus its bandgap energy.

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