2. Jean Baptiste Perrin Nobel Prize in physics 1926 He demonstrated that the current in a vacuum tube was due to electron motion.

3. Collisions of particles affects the mobility term. +- Effective mass!

4. Lattice structure will also vibrate due to T > 0 “lattice scattering”

5. Electron & ion density and conductivity versus temperature -- silicon

6. Typical mobility values Silicon1350480 Gallium arsenide8500400 Germanium39001900

7. Conductivity densities may be different

8. Restrictions in design

9. Exercise 4.3 For a particular silicon semiconductor device at room temperature, the required material is to be n type with a resistivity of  = 0.1  -cm. (a) determine the required impurity doping concentration and (b) the resulting electron mobility. Impurity concentration resistivity

10. Semiconductors are nonlinear. Velocity depends on electric field.

12. Semiconductors are nonlinear. GaAs Velocity depends on electric field.

13. Diffusion current is due to density gradient of density

15. Exercise 4.5 Assume that, in an n-type GaAs semiconductor at T = 300°K the electron concentration varies linearly. Calculate the magnitude of the diffusion current density.

16. Typical values Silicon13503548012.4 Gallium arsenide850020040010.4 Germanium3900101190049.2

17. Diffusion current is due to density gradient of density – nonuniform doping

18. - Diffusion of electrons

21. Exercise 4.6 Assume that the donor impurity concentration In a semiconductor is given by Determine the electric field induced in the material in this impurity concentration.

22. Total current density– 4 components

23. The electron density changes differently than the ion density

24. Einstein relations

26. Due to T > 0, “lattice scattering” This effects mobility & diffusion!

27. National Public Radio puzzle combinations of 2 & 7 & j yields 8

29. Golf course for the elderly