Scottky barrier/ohmic

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:

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

Regards,

KodKodKod Learning Consulting - here you get the answers -

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?

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 -