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reverse biased diode variable resistance experiment

Discussion in 'Electronic Design' started by Jamie M, Dec 2, 2013.

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  1. Jamie M

    Jamie M Guest

    Hi,

    This is related to the "poor mans superconductor wire" thread,
    for testing an idea of anomalous resistance decrease in a diode.

    If you reverse bias a diode, then electrons move closer to the
    junction of the diode as the voltage pressure increases. I was
    thinking maybe this biasing of the electric field will change the
    electrical resistance on each side of the diode. Ie. if the actual
    diode IC die is available to probe, reverse bias the diode, and then
    put two probes on one side of the diode and measure the resistance
    from two points on the anode-anode or cathode-cathode and see if the
    resistance changes based on the level of reverse bias. Any ideas?

    I was thinking about this in the case of topological insulators,
    where with an infinite voltage breakdown diode, eventually it will
    act as a topological insulator in this case and may then act as a
    superconductor in this case.

    cheers,
    Jamie
     
  2. Yeah, they call it a zener diode!
     
  3. Jamie-

    The effect of changing a diode's reverse bias results in junction
    capacitance changing. One Varicap data sheet I checked shows lowering
    capacitance as Voltage increases. I believe the electrons move away
    from the junction as reverse Voltage increases.

    What you describe sounds like an inside-out field effect transistor. I
    can imagine there might be some variation in resistance, but why do you
    think it would be superconductive?

    One problem is that you may not be able to probe such a small area. You
    would need to design a device with molecular-sized electrodes. To use
    the resistance, current must flow, and some of that current might be
    "injected" into the junction. Now it is sounding like an SCR!

    Fred
     
  4. Frank Miles

    Frank Miles Guest

    You may want to read some more about how PN junctions work. The depletion
    region _widens_ with increased reverse bias potential.
     
  5. Robert Baer

    Robert Baer Guest

    * See Chapter 7, Transistors and Active Circuits by J. G. Linvill and J.
    F. Gibbons, MgGraw Hill 1961, especially pp158-173.
    * Perhaps you better read the whole book.
     
  6. Robert Baer

    Robert Baer Guest

    This variable resistance (of a zener diode) was used as a crude high
    voltage shunt regulator for PMTs.
    One manufacturer (Comprobe) of oil well logging sondes utilized
    conventional silicon diodes as high voltage regulator devices. The
    diodes had to be selected for appropriate reverse leakage
    characteristics, a time consuming process resulting in a low yield of
    usable devices. The leaky diode high voltage regulator was unreliable
    and extremely temperature unstable, and its use was long ago discontinued.
     
  7. Jamie M

    Jamie M Guest


    Hi,

    I meant a variable resistance from one section of the anode to another
    section of the anode, (or one section of the cathode to another section
    of the cathode) - but not a variable resistance across the junction.

    I should study more before I post though you are right (thanks!)

    cheers,
    Jamie
     
  8. Jamie M

    Jamie M Guest

    Cool didn't know you can actually use a diode as a JFET (as long
    as you have access to the die to put on another wire)

    cheers,
    Jamie
     
  9. Jamie M

    Jamie M Guest

    Hi,

    I was interested in a theoretical superconducting JFET, ie one that
    doesn't quite fully shut off the current flow, but leaves a surface
    flow of electrons like a topological insulator for zero resistance
    flow.

    cheers,
    Jamie
     
  10. Jamie M

    Jamie M Guest

    Hi,

    In a JFET, if you turn it off, right before it turns off maybe there is
    a nonlinear resistance spike when the resistance goes down right as the
    electrons are only conducting on the very outer area. This would make
    sense as the JFET turns off when the electrons are only conducting on
    the outer surface of the silicon, so at that point the conduction case
    is different than if the electrons were traveling within the silicon.

    Also to keep the fine balance of electric field necessary for only
    surface conduction, right before the JFET is turned off, maybe a light
    could be shone onto the surface to allow surface conduction, even with
    a fully turned off JFET.

    cheers,
    Jamie
     
  11. Robert Baer

    Robert Baer Guest

    Reading a bit of Linvill?
     
  12. Jamie M

    Jamie M Guest

  13. Robert Baer

    Robert Baer Guest

    Yes; in a previous posting,i referred to a particular set of pages in
    his book Transistors and Active Circuits - when responding to musings
    regarding reversed biased diodes and negative resistance.
     
  14. Jamie M

    Jamie M Guest

    Hi,

    I unfortunately don't have the book, sounds interesting though. Might
    take a trip to the library for that one.

    cheers,
    Jamie
     
  15. Jamie M

    Jamie M Guest

    Hi,

    "Pressure transforms a semiconductor into a new state of matter"
    [topological insulator]

    http://phys.org/news/2013-12-pressure-semiconductor-state.html

    In this case they used extreme mechanical pressure, but I think
    voltage pressure could do the same thing for certain materials or
    metamaterials.

    cheers,
    Jamie
     
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