2
\$\begingroup\$

Can a diode be made by connecting, in series, separate n and p-type semiconductors?

Assume that all ends are attached to Ohmic contacts. I am hoping that this will prevent any discontinuities in the potential.

I have seen a similar question on the Physics Stack Exchange, but the question is too old to make comments (https://physics.stackexchange.com/questions/72432/would-connecting-p-type-and-n-type-semiconductors-work-as-a-diode). But in that question, they didn't talk about Ohmic contacts.

Hypothetical Diode

\$\endgroup\$
13
  • 1
    \$\begingroup\$ No, you need P and N doped stuff to physically touch. There forms a barrier. \$\endgroup\$
    – Ilya
    Dec 6, 2021 at 14:26
  • \$\begingroup\$ @Ilya What difference does it make if ohmic contacts are present. The potential at the end of the p-side will continue at the start of the n-side right? \$\endgroup\$ Dec 6, 2021 at 15:49
  • \$\begingroup\$ Where P and N regions touch, there appears a "neutral" zone, small layer of "undoped" (electrically-neutral more like) area that actually forms the barrier. If I simplify it a bit, it's kinda like P and N regions diffuse into one another a little and that forms the barrier. If there is distance between them, it won't work. There are a lot of materials that explain physics inside diodes in relatively simple words (like me but actually correct and smart) \$\endgroup\$
    – Ilya
    Dec 6, 2021 at 15:52
  • \$\begingroup\$ @Ilya So, what about the cases where we (in UG courses) assume PN-junction diodes to have abrupt junctions? (an ideal diode) \$\endgroup\$ Dec 6, 2021 at 16:07
  • 1
    \$\begingroup\$ @Jonathan_the_seagull No, they can't. Holes can't travel through metal, they recombine with electrons immediately. \$\endgroup\$
    – Hearth
    Dec 6, 2021 at 17:29

1 Answer 1

4
\$\begingroup\$

Can a diode be made by connecting, in series, separate n and p-type semiconductors?

No. What you show would behave as 2 resistors in series.

Note that PN junctions in a semiconductor rely on dopings within the same crystal structure, i.e. monocrystalline silicon.

Your picture shows two independent crystals.

\$\endgroup\$
4
  • \$\begingroup\$ But, what about the ohmic contacts? \$\endgroup\$ Dec 6, 2021 at 14:29
  • 1
    \$\begingroup\$ they're just that – ohmic contacts. What you've drawn is really just two separate resistors. (and that's good! Though experiment: we both agree the contact-P+-contact component doesn't do anything special, right? so, why should the whole thing suddenly behave differently when, 2km down the cable, someone attaches a contact-n-contact component? \$\endgroup\$ Dec 6, 2021 at 14:45
  • \$\begingroup\$ @MarcusMüller Do you mean to say that the device will behave like a diode? \$\endgroup\$ Dec 6, 2021 at 15:49
  • 1
    \$\begingroup\$ no, the opposite. \$\endgroup\$ Dec 6, 2021 at 15:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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