0
$\begingroup$

I have a question I am sticking around and can't find a satisfying answer. Say I have an intrinsic semidonductor at zero Kelvin (no electrons in conduction band). I apply a DC voltage across it. Can the electron get excited from the valance band to the conduction band just by the DC voltage? There is band gab for i.e lets say 1 eV of the Semiconductor and there is the relation ΔU = e*ΔV. So the energy per electrons inceases with increasing voltage. Hence, at some point, when high enough voltage is applied, the electrons should be excited to the conduction band and an inmense flow of electrons should occur, right?

Best Regards

Improve this question
$\endgroup$
4
  • $\begingroup$ Depends on whether your criteria includes the material's condition (specifically it's band gap levels) to remain unchanged once conduction begins. Because conduction could occur by bringing electrons to a sufficient energy level, or by permanently reducing the bandgap energy or dieelectric strength in the material. As far as I know (and I don't know much) , there's no law that says a material must be able to support conduction band electrons without damage. $\endgroup$
    – DKNguyen
    Commented Feb 12 at 16:03
  • 1
    $\begingroup$ A large enough voltage gradient will allow tunneling from the valence band to the conduction band. Such a gradient usually does not end well for the material... $\endgroup$
    – Jon Custer
    Commented Feb 12 at 16:18
  • $\begingroup$ Once you've promoted an electron to the conduction band, it is (or at least its electrons are) no longer at 0 K. It might not even be possible to define its temperature. $\endgroup$
    – The Photon
    Commented Feb 12 at 16:46
  • $\begingroup$ @DKNguyen Yes I know that the sample will be damaged or destroyed. I just wanted to understand the concept if applying a DC-bias can excite electrons. I leard that a bias can just bends the band diagram but I also saw discussions that people say with bare voltage can excite electrons. So I am confused what is actually true. $\endgroup$
    – MLSPhy
    Commented Feb 21 at 12:13

1 Answer 1

Reset to default
0
$\begingroup$

Yes, you are right! it is called the Zener effect, which can be considered to be a tunneling of electrons from the valence band into the conduction band through the triangular energy barrier created by the band gap and a high homogeneous electric field. This electron tunneling leaves an equivalent number of holes behind in the valence band (pair creation) and is thus an electron hole pair generation process at high fields.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.