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Image from page 470 of "The Bell System technical journal" (1922) | by Internet Archive Book Images
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Image from page 470 of "The Bell System technical journal" (1922)

Identifier: bellsystemtechni28amerrich

Title: The Bell System technical journal

Year: 1922 (1920s)

Authors: American Telephone and Telegraph Company

Subjects: Telecommunication Electric engineering Communication Electronics Science Technology

Publisher: [Short Hills, N.J., etc., American Telephone and Telegraph Co.]

Contributing Library: Prelinger Library

Digitizing Sponsor: Internet Archive



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Text Appearing Before Image:

Potential Distribution and Capacity or Transition Region 2.1 Introduction and Definitions We shall suppose in this treatment that all donors and acceptors areionized (a good apj^roximation for Ge at room temperature) so that w-e haveto deal with four densities as follows: n = density of electrons in conduction band p = density of holes in valence-bond band Nd = density of donors Xa = density of accej^tors The total charge density is p= q(p- n + Nd - No), (2.1) where q is the electronic charge. We shall measure electrostatic potential\p in the crystal, as shown in Fig. 2, from such a point, approximately mid-way in the energy gap, that if the Fermi level tp is equal to i/, the concentra-tions of holes and electrons are equal to the concentration »,• = pi char- 2 H. Suhl and W. Shocklcy Pliys. Rev. 75 1617 (1949). ^ A difference in effective masses for holes and electrons will cause a shift of \p from themidiKiint between the l)ands. p-n JINCTIO.XS l\ SEMlCONDfCTOKS 439 •I- o^ = y


Text Appearing After Image:

p = ni_e kT [a] INTRINSIC (b) p-TYPE q (v^-^) + + + + q(^^-yn) n = n, e ;,j (C) n-TYPE WITHINJECTED HOLES >?: Fig. 2—Electrostatic potential i/-, Fermi level <p and quasi Fermi levels ifp and <p,,.(In order to show electrostatic potential and energies on the same ordinates. the ener-gies of holes, which are minus the energies of electrons, are plotted upwards in the figuresin this paper.) acteristic of a pure sample. For an impurit}- semi-conductor we shall have,as shown in (b), p = HiC ci{<P-v)lkT n = UiCwhere q is the electronic charge. Accordingly, P = ([[Nd - Xf + 2;7, sinh \q(^ - ^p)/kT]}. (a)(b) (2.2) (2.3) When the hole and electron concentrations do not have their equilibriumvalues, because of hole or electron injection or production of hole-electronpairs by light, etc., it is advantageous to define two non-equilibrium quasiIermi levels <pp and -^n by the equations Hie <i(ippip)lkr (a) „Q<.p-<Pn)lkT (2.4) Hie (b) as indicated in Fig. 2 (c). In terms



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