Notes For 25 February Electron and Hole Concentrations in Extrinsic Semiconductor

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

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

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

4. Variation of Fermi-Energy with Doping Concentration 4 4

5. Variation of Fermi-Energy with Temperature 5 5

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

8. 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 holes Current density due to the electrons Charge density: Drift velocity of electrons Total drift current density 8 8

9. 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 Definition of Carrier Mobility 9 9

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

14. Resistance 14 14