X dt dpx dt field dpx dt collision px tn dpx dt

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Unformatted text preview: at Equilibrium •  Assignments •  Topics for Next Lecture 3 Conduc[vity and Mobility Drih in a Semiconductor Assume uniform distribution of carriers: no diffusion + - 5 Electron and Hole Current Density Rela[onship Electrons: (− q )nEx = dp Holes: qnEx = x dt dpx dt field dpx dt =− collision px tn dpx dt + collision dpx dt =0 field field Electric field causes accelera[on of the group of electrons (holes) in the crystal Interac[on of electrons (holes) with the crystal creates an opposing force to the applied electric field The opposing force from the crystal balances the force due to the applied electric field at some mean value of velocity for the distribu[on of electrons (holes) The mean value of the electron (hole) velocity mul[plied by the electron (hole) density mul[plied by the charge carried and sign of the charge (- /+) gives the current density The rela[onship between the value of the electric field and the mean value of the electron (hole) velocity at that field gives the mobility The mean velocity is the total momentum of all electrons (holes) divided by the total mass of all electrons nŸ༉mn* J x,n = −qn vx = qnµn Ex J x, p = qp vx = qpµ p Ex q tn E x = − µn E x * mn qtp vx =...
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