Hi, you can read the attachment files.

Regards,

Hello Alireza

This is a common situation in the Al_x Ga_(1-x)As ternary alloy system, with sphalerite (=zincblende) structure. For x

Thanks Vincent. In the case of x=x_c, how does the material behave then? Like direct or indirect band gap semiconductor?

From a theoretical standpoint, why does this happen? I am especially puzzled that the CBM line is very much flat (fluctuates within 0.1 eV only between M and K point).

See the attachment. The difference (0.08 eV) is well within the range of numerical error.

Actually the behavior of AlGaAs for around x=x_c is neither that of a purely direct or indirect bandgap semiconductor.

•For transport in bulk AlGaAs material, electron in both CBM, Gamma and X, must be taken into account, as well as those in the L minimum, which is not much higher, and contains also a non-negligible fraction of electrons at room temperature or above.

This leads to a strong dependence on the magnetic field in the Hall effect and magnetoresistance

Due to the much higher effective mass in the 4 X minima, which leads to a much higher DOS and a much lower mobility, these effects can be seen already for x much lower than x_c. Specifically, all 3 types of minima must be taken into account for transport interpretation above room temperature in AlGaAs with x_Al = 0.32 (I recall x_c is around 0.45).

In heterostructures where AlGaAs is used as a barrier, both Gamma and X valleys must be taken into account:

- for calculating 2D subbands (QW) or minibands (superlattices) in parallel transport,

- and for calculating the various tunnel probabilities in perpendicular transport.

•For optical effects, the presence of a lot of electrons in the indirect minima strongly affects the radiative transition rate.

•In your material, if the rather flat conduction band between M and K is real, then it might have among others funny effects in magnetotransport.