Are these EDP curves correct?

[lknife]

Hi, experts,

I got an interface-based device and I wanted to check the length of the device by plotting the ElectrostaticDifferencePotential (EDP) curve of this device. I got two EDP curves, one was for the original device and the other was for the device with doping.  However, the EDP for the doped device is far from an ordinary one, I think. Please see the attached pictures and the python file for EDP calculation.

I want to know: if there is something wrong with the EDP curves, what made the EDP curve for the doped device look like this ?

Thanks very much for your kind help!
 

[Daniele Stradi]

Hi,

by doping, do you mean explicit doping by including dopant atoms in the structure? The HDP looks reasonable, and it shows that the charge redistribution is different between the two systems.
Also, notice that, apart from the oscillation due to the atomic cores, the potential should be flat close to C = 0.0 and C = 1.0.

Regards,
Daniele.

[lknife]

Thank you very much, Mr. Daniele Stradi!

I introduced doping by using the "doping" plugin, not including dopant atoms in the structure.

How did you think that the HDP is reasonable? Did you run the calculation and plot the HDP curve of it? I haven't done that yet since I am not sure of the abnormal oscillation of the EDP curve for the doped device.

I know that the potential should be flat close to the electrodes. Since it's not so flat for the original device and I don't want to make the device longer, I added doping in order to make it flatter. However, it didn't seem successful. Moreover,  I didn't expect to get an EDP curve like the one for the doped device.

[lknife]

I calculated the hdp curve for the doped device, seen in the attached picture. However, I don't think it's an ordinary one because of the oscillations.

I also calculated the EDP and hdp curves for the device with opposite doping: that is , the previously mentioned doped device was set to n-p doping while the new doped device was set to p-n doping. The EDP and hdp curves are also attached here. Could you please help me to see if there is something wrong with these curves?

Also, do you think the EDP is flat enough near the electrodes for the p-n doping device?

Thanks a lot for your kind help!

[Daniele Stradi]

Hi,

The potential looks flat-enough. However, I agree that the behavior of this device is quite weird, and I think it is mostly related to the fact that the device is very short, even including doping.
For bulk silicon, the depletion region at the doping that you have considered is around 20 nanometers. For a 2D material, screening will be less effective, and therefore the depletion region will be even larger.
If you don't want to increase further the size of the device, the only solution would be to keep increasing the doping, until the potential in the central region is fully screened. But since your device is very short, you might need to go to quite large values of doping.

Regards,
Daniele

[lknife]

Thank you very much, Mr. Daniele Stradi! I'll take your valuable advice seriously.

Thank you again for your kind help! Wishing to learn more from you in the future!