a question about diode？

xunrichard

As we are told in the books，a diode can be conductive by a forward-bias of about 0.7v.
Thus,current through the n region is formed by the conduction electrons（free electrons in the conduction band） toward the junction.But in the p region,current is formed by the valence electrons from holes to holes toward the positive side of the power source.Obviously,the conduction electrons from the n region can easily become the valence electrons in the p region and the valence electrons in the p region can easily become conduction electrons so they can move into the copper cord（as we suggest）which is between the positive side of the power source and the p region.
So here is the question：why a diode can not be conductive by a reverse-bias voltage?
Can the conduction electrons in the copper cord move into the p region? If not,why?

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Jiggy-Ninja

Positive voltage on the N region pulls free electrons away from the junction.

Negative voltage on the P region pulls holes away from the junction. Alternately, you can think that the negative voltage pushes electrons in to fill the holes by the junction.

The junction is left barren of any charge carriers, and only the barest trickle of current can flow through.

dlgoff

They can. See metal–semiconductor (M–S) junction

But ...



See Band Theory of Solids

xunrichard

Thank you! You are right. I think I got it.Thank you.

xunrichard

Thank you,dlgoff! That's a different way to think about it.But I don't know whether it is a
metal-semiconductor junction.