1. Mobile Carrier Action Reading Assignment Pierret : Chap 2 and Chap 3 Instructor: Prof. Dr. Ir. Djoko Hartanto, M.Sc. : Arief Udhiarto, S.T, M.T Source: Source: Professor Nathan Cheung, U.C. Berkeley

2. Electrical Engineering Department University of Indonesia 2 Carrier Concentration vs Temperature

3. Electrical Engineering Department University of Indonesia 3 Dependence of E f on Temperature

4. Electrical Engineering Department University of Indonesia 4 Degenerate Semiconductors If dopant concentrations are very high such that E F is < 3kT from E C or E V, we have to to use the full Fermi-Dirac probability function

5. Electrical Engineering Department University of Indonesia 5

6. 6 Electron as Moving Particle

7. Electrical Engineering Department University of Indonesia 7 Semiconductor Carriers Effective Mass

8. Electrical Engineering Department University of Indonesia 8 Carrier Scattering Because of scattering, mobile cariers in a semiconductor do not achieve constant acceleration. However, they can be viewed as classical particles moving at a constant average drift velocity 1) “Lattice Vibration (phonons) scattering” -No dopant dependence -Increases with increasing temperature 2) Ionized impurity scattering -Increases with N A +N D (total dopant conc) -Decreases with increasing temperature

9. Electrical Engineering Department University of Indonesia 9 Carrier Drift With an electric field, mobile charge-carriers will be accelerated by the electrostatic force. This force superimposes on the random thermal motion of electrons:

10. Electrical Engineering Department University of Indonesia 10 The average current in any direction is zero, if no electric field is applied Electrons drift in the direction opposite to the E – field  Current flows

11. Electrical Engineering Department University of Indonesia 11 Electron Momentum With every collision, the electron loses momentum With every collision, the electron loses momentum Between collision, the electron gains momentum Between collision, the electron gains momentum

12. Electrical Engineering Department University of Indonesia 12 Balancing momentum gain and momentum lost

13. Electrical Engineering Department University of Indonesia 13 Mobility Dependence on Doping

14. Electrical Engineering Department University of Indonesia 14 Electrical Conductivity σ When an electric field is applied, current flows due to drift of mobile electrons and holes:

15. Electrical Engineering Department University of Indonesia 15 Electrical Resistivity ρ

16. Electrical Engineering Department University of Indonesia 16 Electrical Resistance

17. Electrical Engineering Department University of Indonesia 17 Example

18. Electrical Engineering Department University of Indonesia 18 Example (continued)

19. Electrical Engineering Department University of Indonesia 19 Temperature Effect on Mobility

20. Electrical Engineering Department University of Indonesia 20 Example: Temperature Dependence of ρ

21. Electrical Engineering Department University of Indonesia 21 Diffusion Current

22. Electrical Engineering Department University of Indonesia 22 Diffusion Current Density ( Fick’s First Law)

23. Electrical Engineering Department University of Indonesia 23 Total Current Density