Notes For 25 February Electron and Hole Concentrations

Notes For 25 February Electron and Hole Concentrations in Extrinsic Semiconductor For both undoped material and doped material under equilibrium condition 1

Position of Fermi Energy in Extrinsic Semiconductors Position of Fermi-level: 2

Position of Fermi Energy in Extrinsic Semiconductors Position of Fermi-level: 3

Variation of Fermi-Energy with Doping Concentration 4

Variation of Fermi-Energy with Temperature 5

Chapter 5 Carrier Transport Phenomena Charged carriers in semiconductor: electrons and holes Carrier transport: movement of electrons and holes Drift: charge movement due to electric field Mechanisms of carrier transport Diffusion: charge movement due to density gradient 6

Carrier Drift Observe that the text uses “e” instead of “q” as a symbol for a unit of charge Drift current density Current density due to the holes Charge density: Drift velocity of holes Current density due to the electrons Charge density: Drift velocity of electrons Total drift current density 8 8

Definition of Carrier Mobility: relates the average drift velocity of a carrier to the electric field Drift velocity of holes Drift velocity of electrons : mobility of holes : mobility of electrons 9

Conductivity: Resistivity: Unit: (Ω. m)-1 Unit: (Ω. m) Intrinsic semiconductor: N-type semiconductor: P-type semiconductor: 10

Resistance 14