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Homework Help: Semiconductor analysis.

  1. Jan 12, 2014 #1
    The question asks for a pn junction, calculate the total bending through energy at zero bias of the conduction band edge passing from neutral n-type section to the neutral p-type section.

    Additional info:

    Band gap of silicon Eg = 1.1 eV
    Density of states at conduction band (Nc) = 2.8e19 states/cm^3
    Density of states at valence band (Nv) = 1e19 states/cm^3
    p-type contains 5e16 holes/cm^3 (p)
    n-type contains 1e19 electrons/cm^3 (n)
    Boltz constant k = 8.614e-5 eV/K
    temperature = 300K

    My ans:

    qV_bi = Eb - ∂1 - ∂2, where ∂1 = (Ef-Ev) and ∂2 = (Ec-Ef)

    if holes p = Nv*exp[-(Ef-Ev)/KT] = Nv*exp[-∂1/KT]

    and electrons n = Nc*exp[-(Ec-Ef)/KT] = Nc*exp[-∂2/KT]

    then ∂1 = KT*ln[Nv/p]
    and ∂2 = KT*ln[Nc/n]

    therefore qV_bi = EG - {KT*ln[Nv/p]} - {KT*ln[Nc/n]} = 0.62V

    Is this correct? :confused:
    Last edited by a moderator: Jan 13, 2014
  2. jcsd
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