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QuantumATK => General Questions and Answers => Topic started by: tara on February 25, 2015, 06:31

Title: Screening length
Post by: tara on February 25, 2015, 06:31

Sir

1. What would be screening length of silicon with a doping of 1e19??
I read in the tutorial  http://quantumwise.com/publications/tutorials/item/828-silicon-p-n-junction,that i need a longer device (upto 14nm) as silicon has along  screening length.So if my (all-silicon) device is 10nm long,it would give me incorrect results??

2. In the tutorial  http://quantumwise.com/publications/tutorials/item/820-ni-silicide-si-interfaces, it is mentioned that if we are using doping concentration  from 5e19 to 1e20, it would require silicon region to be 30 to 50A wide.If i am using a doping of 1e19, how much should be the  minimum  width of central silicon region??

Title: Re: Screening length
Post by: Umberto Martinez on February 25, 2015, 07:56

For both answers... yes you will need a longer device for 1e19 doping level. More or less around 10nm as you say (see graph in the tutorial).
To know if this is indeed enough you can plot the electrostatic potential across your device and verify, as the tutorials indicate, that your potential is fully screened, i.e. flat at the electrode boundaries. If not increase the length until you are satisfied.
Using a shorter device (well, it depends how much shorter) may give you qualitatively ok results, it's not possible to predict.
I suggest you to use a proper length.

Title: Re: Screening length
Post by: tara on February 25, 2015, 08:29

In the tutorial , http://quantumwise.com/publications/tutorials/item/820-ni-silicide-si-interfaces

Does the Width of the device refer to  broadness of the device (in Y -direction)??

Title: Re: Screening length
Post by: Umberto Martinez on February 25, 2015, 08:41

oh, I see it can be confusing.
no, it refers to the dimension in Z direction, the length of the central region.
the device is periodic in y and x.