[Pw_forum] metal-semiconductor interface

[Sridhar Sadasivam]

Hello,

This is not exactly a question on QE but a general question on computing
electrostatic potential near a metal-semiconductor interface using DFT. I
would really appreciate thoughts from the QE community.

There exists a lot of DFT papers that plot the electrostatic potential near
a metal-semiconductor interface and use it to obtain the Schottky barrier
height. Here's one such example where the authors work with a RhSi (metal)
- Si interface:
http://scitation.aip.org/content/aip/journal/jap/112/9/10.1063/1.4761994 You
will notice from Figure 3 in that paper that the average electrostatic
potential (average over each sinusoidal oscillation) becomes constant in
the semiconductor within a small length (~ 5 Angstrom) away from the
interface. I have seen this in many other papers and in my own
calculations.

However, for an undoped semiconductor (no screening), the potential is not
expected to become constant for at least a few tens of nm away from the
interface (example:
http://www.nextnano.de/nextnano3/tutorial/1Dtutorial_Schottky_barrier.htm
 ).

I'm trying to understand why DFT predicts a very small screening length
even for undoped semiconductors. I am wondering if this is a DFT limitation
and thought someone might have some idea on this? I would really appreciate
any thoughts.

Thank you!
Sridhar
Purdue University
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