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Scottky barrier/ohmic

P

PZ

Jan 1, 1970
0
Reading it for a while, still don't understand when is
blocked/non-blocked. Blocked means no current passing through? blocked
means no free carrier?
 
K

KodKodKod Learning Consulting

Jan 1, 1970
0
Hi,

A Schottky barrier means that the current can flow from one direction
but not the other. As a result, its current-voltage characteristic is
just that of a diode. So, it is blocking in one direction and
non-blocking in another. For example, usually, if a metal is in contact
with an n-type semiconductor, current can flow from metal to n-type but
not from n-type to metal (of course, it means electron can flow from n
to metal but not from metal to n).

However, if we heavily dope the semiconductor (e.g. >1E20cm^-3), now
the barrier is very thin and quantum tunneling is possible. Then there
is no blocking behavior and the current can flow in both direction.
This is Ohmic now.

If you want to know more about Schottky barrier, you may refer to our
database:

http://www.kodkodkod.com/files/thermionic.htm

Here you will know why a schottky barrier behaves like a diode.

Regards,

KodKodKod Learning Consulting - here you get the answers -
www.kodkodkod.com
To submit questions: http://www.kodkodkod.com/index_files/Page582.htm
 
P

PZ

Jan 1, 1970
0
thanks for your reply.


then in the band diagram, why "ohmic" bends down, and "blocking" bend
up, interms of x=0? and why in "blocking", the charge at Si is
rectangle, but in "ohmic", it is curve?
 
K

KodKodKod Learning Consulting

Jan 1, 1970
0
The bending is due to the formation of depletion charge. And the
depletion width is

Xd ~ sqrt(1/N_D), so the larger the doping concentration, the smaller
the depletion width. Therefore, if it is heavily doped, the width is
very small and quantum tunneling is possible. And if it is lightly
doped, the width is larger.

Indeed, both are parabolic and both bend down. But for ohmic, it is so
small that it looks like a "narrow" triangle. and for schottky, it
looks like a rectangle.

Regards,

KodKodKod Learning Consulting - www.kodkodkod.com
 
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