Understanding AlGaAs/GaAs Band Gap and Conduction Band Offset Variations

[daffoddill]

how the conduction band offset varies with Al concentration?? what is the different?

 

[nickjer]

This is a very vague question. If you want specific numbers you will have to read journal articles on experiments that measure conduction band offsets. If you want a qualitative answer, you know AlAs/GaAs is a type I band offset, with AlAs having the larger band gap. And when you have GaAs/GaAs, there is no offset. So as you increase Al concentration, the CBO will increase all the way to the max CBO of AlAs/GaAs. To find the exact form of the increase in the CBO you need to read journals.

 

[daffoddill]

let say for AlGaAs/GaAs/AlGaAs structure, why Al increases the conduction band offset in this case?

do you have any suggestion about the link that i can access to the journal? There's a lot of them but need to pay.

 

[nickjer]

I just told you why Al increases the CBO. Since it increases the band gap, and you also know the initial % Al = 0 then CBO = 0 and the final % Al = 1 then CBO > 0. Therefore as you increase Al concentration you must increase the CBO.

As for the journals, I can't help you there.

 

[paranormal]

The band gap and conduction band offset variations in AlGaAs/GaAs heterostructures are important factors to consider in the design and optimization of electronic and optoelectronic devices. The band gap and conduction band offset are both influenced by the concentration of Al in the AlGaAs layer.

The band gap is the energy difference between the valence band and the conduction band, and it determines the material's ability to absorb and emit photons. As the Al concentration increases, the band gap of AlGaAs increases, resulting in a wider band gap compared to GaAs. This is due to the larger atomic size of Al compared to Ga, which leads to a larger lattice constant and a larger band gap.

The conduction band offset, on the other hand, is the energy difference between the bottom of the conduction band in the AlGaAs layer and the bottom of the conduction band in the GaAs layer. It is an important parameter in determining the electron transport properties at the AlGaAs/GaAs interface. As the Al concentration increases, the conduction band offset decreases, meaning the conduction band in the AlGaAs layer moves closer to the conduction band in the GaAs layer.

This variation in conduction band offset with Al concentration has important implications for device performance. A larger conduction band offset can lead to a higher barrier for electron transport, resulting in better confinement of electrons in the active region of a device. On the other hand, a smaller conduction band offset can result in a lower barrier and better electron transport across the heterojunction.

In summary, the band gap and conduction band offset variations in AlGaAs/GaAs heterostructures are closely related to the concentration of Al in the AlGaAs layer. Understanding and controlling these variations is crucial for the design and optimization of electronic and optoelectronic devices.