Understanding Diode Conductivity: The Role of Conduction and Valence Electrons

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A diode conducts when forward-biased at approximately 0.7V, allowing conduction electrons from the n-region to move toward the junction, while valence electrons in the p-region move toward the positive side of the power source. In reverse-bias, the positive voltage on the n-region pulls free electrons away from the junction, and the negative voltage on the p-region pulls holes away, leaving the junction devoid of charge carriers and limiting current flow. The discussion raises questions about whether conduction electrons from the copper cord can move into the p-region, which they can, as explained by metal-semiconductor junction principles. However, the complexities of band theory and the specifics of the junction type are acknowledged as areas needing further clarification. Understanding these principles is crucial for grasping diode functionality.
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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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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 into 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.
 
Jiggy-Ninja said:
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 into 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.

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

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