P-N junction charge utilisation

[messysmurf]

Hello,

A depletion region forms instantaneously across a P-N junction. When N-doped and P-doped pieces of semiconductor are placed together to form a junction, electrons migrate into the P-side and holes migrate into the N-side. As such, in the depletion region, the P-side becomes negatively charged with respect to the N-side which is positively charged,

If an external conductor is made to connect the P and N areas of the depletion region, then a current must flow as there is a potential difference between the N and P areas of the depletion region. The effect of such conductance is to cause the charge difference, in the depletion region, between the N and P doped materials to diminish.

My question is, will the P-N junction spontaneously tend to replenish the charge difference between the P and N doped pieces and hence cause current to continuously flow in the external conductor? Alternatively, if the conductor is periodically attached and detached, will this allow the spontaneous formation of charge separation to be utilised to generate current?

Regards, Tim.

 

[eljose79]

Dear Tim,

Thank you for your question. The answer to your question depends on the specific conditions and materials of the P-N junction. In general, a P-N junction will tend to replenish the charge difference between the P and N doped pieces, but the rate at which this happens can vary.

If the external conductor is continuously connected, the depletion region will eventually reach a steady state in which the charge difference between the P and N sides is maintained, and no further current will flow. This is because the flow of charge is balanced by the flow of electrons and holes in opposite directions.

However, if the external conductor is periodically attached and detached, this can create a cyclical process of charge separation and depletion region formation. This can be utilized to generate a current, but the efficiency of this process will depend on the materials and conditions of the junction.

It is also important to note that the depletion region will not continuously replenish the charge difference indefinitely. The amount of charge separation is limited by the amount of doping in the materials and the strength of the electric field in the junction. Once these limits are reached, the depletion region will reach a steady state and no further current will flow.

I hope this helps to answer your question. If you have any further inquiries, please don't hesitate to ask.