Why is the absorption depth for GaAs more than for Germanium?

In summary, the conversation discusses the value of the edge coefficient for Germanium and GaAs at different wavelengths and the discrepancy between the optimal thickness of the two materials based on the theory of absorption depth. The participants also question if Ge should be more transmissive than GaAs at a specific wavelength.
  • #1
A Sofyan
It is based on the value of the edge coefficient I obtained, for Germanium at the wavelength of 1550 nm has a value of 459.54 / cm and GaAs at wavelength 885.6 nm has a value of 239.78 / cm.

If based on the theory of absorption depth (1 / alpha), then the optimal thickness of GaAs is thicker than Ge, and to my knowledge, this seems to be wrong in the application, can anyone explain? Is there something wrong with my understanding?
 
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  • #2
Both materials, if I'm not mistaken, are in a transition from being opaque at shorter wavelengths to starting to become transmissive at 1550 nm. Is there any reason you think Ge should be more transmissive than GaAs at this particular wavelength?
 
  • #3
Charles Link said:
Both materials, if I'm not mistaken, are in a transition from being opaque at shorter wavelengths to starting to become transmissive at 1550 nm. Is there any reason you think Ge should be more transmissive than GaAs at this particular wavelength?
It is based on the value of the edge coefficient I obtained, for Germanium at the wavelength of 1550 nm has a value of 459.54 / cm and GaAs at wavelength 885.6 nm has a value of 239.78 / cm.
 

Related to Why is the absorption depth for GaAs more than for Germanium?

1. Why is the absorption depth for GaAs greater than for Germanium?

The absorption depth for a material refers to the distance that light can penetrate into the material before being fully absorbed. In the case of GaAs and Germanium, the absorption depth for GaAs is greater because it has a wider bandgap compared to Germanium. This means that GaAs can absorb light of higher energy (shorter wavelength) than Germanium, resulting in a longer absorption depth.

2. How does the bandgap of a material affect its absorption depth?

The bandgap of a material plays a crucial role in determining its absorption depth. A wider bandgap means that the material can absorb light of higher energy, resulting in a longer absorption depth. On the other hand, a narrower bandgap allows the material to absorb light of lower energy, resulting in a shorter absorption depth.

3. What other factors besides bandgap can affect the absorption depth of a material?

Apart from bandgap, the absorption depth of a material can also be influenced by its density and crystal structure. Materials with higher density and a more ordered crystal structure tend to have longer absorption depths due to their ability to efficiently absorb and scatter light within the material.

4. How does the absorption depth of GaAs and Germanium impact their use in optoelectronic devices?

The difference in absorption depth between GaAs and Germanium has significant implications for their use in optoelectronic devices. GaAs, with its longer absorption depth, is better suited for high-energy applications such as solar cells, LEDs, and laser diodes. On the other hand, Germanium's shorter absorption depth makes it more suitable for low-energy applications such as infrared detectors and optical fibers.

5. Can the absorption depth of a material be modified?

Yes, the absorption depth of a material can be modified by changing its composition, structure, or doping. For example, by alloying GaAs with other materials, its bandgap can be tuned, resulting in a different absorption depth. Additionally, introducing defects or impurities into the material can also alter its absorption properties.

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