Properties of Extrinsic Semiconductors

Discussion in 'General Electronics Chat' started by jaydnul, Jun 26, 2015.

  1. jaydnul

    Thread Starter Member

    Apr 2, 2015
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    How does a single slab of p/n-type semiconductor act under a voltage? Does it just have a series resistance? Does it have a defined voltage drop?

    Also why is this used in a Hall Effect sensor instead of just a normal resistive or conductive material? The magnetic field would displace the moving charge in the same way, would it not?

    Thanks a bunch!
     
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    The voltage is caused by charge displacement across the thin conductor ribbon from the magnetic field (similar in principle to the deflection in a CRT tube) so metallic conductors with normally low sensitivity can be used (mainly electron flow but with 'hole' flow in some metals) but semiconductors can also have current flow from 'holes' (electromagnetic forces in the exact opposite direction), the Hall voltage produced is proportional to the mobility of the charges (easily controlled in a semiconductor by modifying the crystal lattice structure by doping) and develop a positive Hall coefficient for current flow in p types.

    http://farside.ph.utexas.edu/teaching/302l/lectures/node74.html

     
    Last edited: Jun 26, 2015
  3. jaydnul

    Thread Starter Member

    Apr 2, 2015
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    K, I understand. The less mobile charge carriers, the stronger the Hall voltage.

    But what does a doped semiconductor act like under a normal voltage at its ends? Is it basically a resistor? Does the resistance change with the number of charge carriers?
     
  4. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    It's a lot more complex than just that but yes, it's basically a resistor but one that sensitive to doping density that changes the bulk mobility.
    http://ecee.colorado.edu/~bart/book/mobility.htm#resistivity
     
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