Why is the band gap in alloys such as GaAs less?

Thread starter Engineer1
Start date May 1, 2019
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Band Band gap Electrical & electronic enging Gap Material science Semiconductor devices

In summary, a band gap in alloys is the energy difference between the valence band and the conduction band in a material. This plays a crucial role in determining the electrical and optical properties of the material. The band gap can be less in alloys than in pure materials due to bandgap bowing, where the energy levels of the individual atoms shift when combined. The band gap affects properties such as conductivity and light absorption, making it important for applications like solar cells and LEDs. It can be engineered by controlling the composition of the alloy, but other factors such as strain, temperature, and defects can also influence it.

May 1, 2019

Engineer1

Gold Member

TL;DR Summary: Why is band gap in alloys such as GaAs less in comparison with intrinsic semiconductor crystals, such as Silicon?

In pure crystals,such as,in silicon and germanium,the band gap is more than that in compound semiconductors,such as,GaAs.Why is that so.

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May 1, 2019

phyzguy

Science Advisor

This is simply wrong. Try looking at the table of band gaps at this Wikipedia page. Silicon is 1.14 eV. GaAs is 1.43 eV. GaN is 3.4 eV. Other compound semiconductors have band gaps less than silicon.

1. Why is the band gap in alloys such as GaAs less than in pure materials?

The band gap in alloys is less than in pure materials due to the presence of impurities or defects in the crystal structure. These impurities create energy levels within the band gap, reducing its size and making it easier for electrons to transition from the valence band to the conduction band.

2. How does the composition of an alloy affect its band gap?

The composition of an alloy plays a significant role in determining its band gap. As the concentration of impurities or defects increases, the band gap decreases. This is because more energy levels are created within the band gap, making it easier for electrons to move between the valence and conduction bands.

3. Can the band gap in alloys be controlled?

Yes, the band gap in alloys can be controlled by adjusting the composition of the alloy. By carefully selecting the types and concentrations of impurities, the band gap can be tuned to meet specific needs for different applications.

4. Why is a smaller band gap desirable in some applications?

A smaller band gap is desirable in some applications because it allows for easier movement of electrons, making the material more conductive. This can be useful in electronic devices such as transistors, where fast and efficient electron movement is necessary.

5. Are there any disadvantages to having a smaller band gap in alloys?

Yes, there can be disadvantages to having a smaller band gap in alloys. A smaller band gap means that the material is more conductive, which can lead to increased power consumption and heat generation in electronic devices. Additionally, a smaller band gap may also make the material more susceptible to degradation and failure over time.