The problem of calculated curent

[fan0221]

Hi, everyone!
I have done a calculation on a  2 dimensional semiconductor system by ATK13.8  with different   lengths. The calculated transmission sepectra show that  the transmission  coefficients of the long system is lower than the short system. It is easy to understand.  However, the calculated currents  are almost same under the same bias voltage. Is there anything wrong with my calculation?
 

[Daniele Stradi]

Dear fan0221,

The current in both system is essentially zero, (~10-4 nA), because your bias window (-0.25 V to +0.25 V) lies within the semiconductor band gap. It is difficult to say more without having a look at how the actual device configuration looks like. However, by looking at the transmission curves, it looks like to have an appreciable current, you should increase the bias voltage quite a lot, so that some of the peaks in the transmission spectrum lies within the bias window (this might be difficult, depending on the system).

best regards,
Daniele.
 

[fan0221]

Dear Daniele Stradi,

Thanks very much for your kind reply.

I do not understand why the current are almost same. The transmission coefficents of the l-system in the bias windows are much lower than that of S-system.

[Jess Wellendorff]

Yes, they are larger, but still extremely small. You should consider them zero within numerical accuracy.

[fan0221]

Thanks very much for your kind reply.