F2010_ECE132_Quiz3_Fri - ECE 132 Quiz 3 Name An intrinsic...

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Unformatted text preview: ECE 132 Quiz 3 Name __________________________ October 22, 2010 An intrinsic semiconductor has been selected which has its intrinsic Fermi level Ei at the center of the bandgap EG, and EG ≈ 40kT. It is doped with two different kinds of donor atoms. The first donor at concentration ND has ionization energy (EC – ED1) = 0.1kT. The second donor at the same concentration ND has ionization energy (EC – ED2) = ΔE2 = 10kT. EG≈40kT Ec EG/2 I Ec II 10kT 0.1kT ED1 ED2 Ei III E v (Intrinsic) Ev (Doped) Energies NOT drawn to scale. 1) Is the doped material n‐type or p‐type? N‐type: n0 > p0; P‐type: p0 > n0. 2) In the doped material, is the Fermi level EF > Ei or is EF < Ei ? 3) In the doped material, do you expect to find EF in region I, II, or III? Justify your answer. The relevant equations are provided below to help you, but you should probably not attempt to directly solve them for EF. f (E) = 1+ e 1 E − EF kT ; n0 + NA‐ = p0 + ND+; NA‐ = NA ∙ f(EA); ND+ = ND ∙ (1 ‐ f(ED)) ...
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