Question

Do carriers move across a p-n junction at $0\ \mathrm{K}$?

Answer 1

Often a band diagram is used to explain what happens when two pieces of the same semiconductor, one p-doped, one n-doped, are put together. I am a little confused about it, so here is my question.

Initially and at 0 K0 K, the surplus carriers should be confined to their respective acceptor and donor levels, e.g. the flatband diagram would look like follows:



Now, there are no free carriers in the system and thus, the electrons from the donor level should not be able to recombine with the holes from the acceptor levels due to spatial detachment. Of course, provided some temperature, the acceptor and donor carriers would ionize and free carriers would be at disposal for recombination and thus, a depletion zone would form. But at 0K it seems to me that this should not happen. In reality, would a depletion zone be formed anyway somehow (are there other relevant physics taking action)?

Answer 2

Zero Biased PN Junction Diode. The potential barrier that now exists discourages the diffusion of any more majority carriers across the junction. However, the potential barrier helps minority carriers (few free electrons in the P-region and few holes in the N-region) to drift across the junction.