Direct and Indirect Optical Band Gap

In summary, the conversation discusses the search for an equation to determine the values of direct and indirect optical band gaps. The difference between these types of band gaps is also mentioned, along with a specific equation related to optical band gap and wavelength at absorption edge. The conversation also suggests seeking further information from a specific physics forum and provides a resource for understanding energy bands in semiconductors.
  • #1
Donchay
10
0
I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap?

also

Does anybody recognised this equation

Eg=hω/λae

where Eg= optical band gap , λae= wavelength at absorption edge

Please enlighten me.

Thanks.
 
Physics news on Phys.org
  • #2
This question is more apt for the atomic, solid state and computational physics forum.
 
  • #3
this is reminiscent of direct bandgap vs indirect bandgap semiconductors ...

The energy bands are plotted in momentum-space and look like wavy lines
Good explanation and examples are shown here

http://www.doitpoms.ac.uk/tlplib/semiconductors/direct.php

Silicon is an indirect band gap semiconductor with a 1.1 eV bandgap width; it is too narrow to emit in the visible and also indirect, which requires a also phonon if an infrared photon is to be emitted.
 
  • #4
Thread has been moved.

Zz.
 

1. What is the difference between direct and indirect optical band gap?

The direct and indirect optical band gap refer to the ways in which electrons move between energy levels in a material. In a direct band gap material, the highest energy level of the valence band aligns with the lowest energy level of the conduction band, allowing electrons to easily transition between the two. In an indirect band gap material, there is a small energy difference between the highest energy level of the valence band and the lowest energy level of the conduction band, making it more difficult for electrons to transition between the two.

2. How does the band gap affect the optical properties of a material?

The band gap is a crucial factor in determining the optical properties of a material. In direct band gap materials, electrons can easily transition between energy levels by emitting or absorbing photons, making them efficient at emitting or absorbing light. In indirect band gap materials, the process is less efficient, resulting in weaker absorption and emission of light.

3. What are some examples of materials with direct and indirect band gaps?

Silicon is an example of a material with an indirect band gap, while materials such as gallium arsenide and indium phosphide have direct band gaps. In general, III-V and II-VI semiconductors tend to have direct band gaps, while group IV semiconductors like silicon and germanium have indirect band gaps.

4. How can the band gap be controlled in a material?

The band gap of a material can be controlled by altering its composition, crystal structure, or doping. For example, adding impurities to a semiconductor can change its band gap, as can growing thin films of a material with a different crystal structure. Additionally, applying an external electric field can also modify the band gap of some materials.

5. What are the practical applications of direct and indirect band gap materials?

Direct band gap materials are commonly used in optoelectronic devices such as LEDs, solar cells, and lasers due to their efficient emission and absorption of light. Indirect band gap materials are often used in electronic devices such as transistors and integrated circuits, as their lower band gap makes them better suited for conducting electricity. Additionally, the ability to control the band gap of a material allows for the design of materials with specific optical and electronic properties for various applications.

Similar threads

What is the energy gap of Titanium Nitride (TiN) and is it indirect or direct?
    • Atomic and Condensed Matter
Replies
1
Views
5K
I Relationship between the depletion region and the band gap of a diode?
    • Atomic and Condensed Matter
Replies
3
Views
5K
A Nanowire with charge neutrality in band gap
    • Atomic and Condensed Matter
Replies
1
Views
1K
How to Determine Band Gap of Amorphous Materials Using Optical Absorption Edge
    • Atomic and Condensed Matter
Replies
3
Views
7K
I How to get plot (optical gain of GaAs)?
    • Atomic and Condensed Matter
Replies
2
Views
3K
I Phonon energy in absorption of indirect band gap
    • Other Physics Topics
Replies
1
Views
1K
I Band theory and qualitative character of bands
    • Atomic and Condensed Matter
Replies
4
Views
2K
I Cyclotron resonance and Landau Levels
    • Atomic and Condensed Matter
Replies
4
Views
2K
Absorption of photons with less energy than the band gap
    • Atomic and Condensed Matter
Replies
4
Views
5K
Effective Mass in Indirect Band Gap Semiconductors
    • Atomic and Condensed Matter
Replies
3
Views
3K

Hot Threads

Recent Insights

Back
Top