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V_n equaion question on PN junction

  1. May 22, 2010 #1
    the formula for Vn should be
    V_n=(E_f-E_i)/q

    field divided by charge in the potential
    like i was taught in high school
    but why
    the write it
    V_n=(E_f-E_i)/KT

    k in the boltsman constant
    t is the temprature

    there multiplication cannot be the charge

    ?
     
  2. jcsd
  3. May 22, 2010 #2
    Hello nhrock3,

    There is a small misconception here.

    When we write [tex]V_n=\frac{E_f-E_i}{kT}[/tex], E for energy; specifically the energy level in the energy band diagram. In such sense the term V_n is dimensionless.

    If I'm getting you wrong, could you please reference your equation or state the full equation so I can get a better understanding.

    Regards
     
  4. May 22, 2010 #3

    uart

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    Science Advisor

    No that does not have dimensions of voltage. You would have to show the context in which it's used but I would assume it is the dimensionless ratio of [itex]V/V_T[/itex], where [itex]V_T[/itex] is the temperature dependant "constant" [itex]kT/q_e[/itex] (approx 26 mV at room temperature).
     
  5. May 29, 2010 #4
    I am using a keithley system for my four probe measurements.I am getting confused with th
     
  6. May 29, 2010 #5
    I am using a keithley system for my four probe measurements.I am getting confused with the curre
     
  7. May 29, 2010 #6
    I am using a keithley system for my four probe measurements.I am getting confused with the current from outer two probes .Since we require a constant current source for that.My problem is that as we are forcing current from outer two probes the system is asking for voltage input.How can it be possible to set any voltage as we are targeting to force current and want to measure from inner two probes.Also if we enter different voltages in that coloumn we are different sheet resistivity.But to the best of my knowledge sheet resisitivity of a material is fixed.

    Please help me urgently on this
    as i have to complete my project on time
     
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