Jean Baptiste Perrin Nobel Prize in physics 1926

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

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

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

Electron & ion density and conductivity versus temperature -- silicon

Typical mobility values Silicon 1350 480 Gallium arsenide 8500 400 Germanium 3900 1900

Conductivity densities may be different

Restrictions in design

resistivity 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

Semiconductors are nonlinear. Velocity depends on electric field.

Semiconductors are nonlinear. Ga. As Velocity depends on electric field.

Diffusion current is due to density gradient of density

Diffusion current is due to density gradient of density

Exercise 4. 5 Assume that, in an n-type Ga. As semiconductor at T = 300°K the electron concentration varies linearly. Calculate the magnitude of the diffusion current density.

Typical values Silicon 1350 35 480 12. 4 Gallium arsenide 8500 200 400 10. 4 Germanium 3900 101 1900 49. 2

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

Diffusion of electrons -

Diffusion of electrons

Diffusion of electrons

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.

Total current density– 4 components

The electron density changes differently than the ion density

Einstein relations

Einstein relations

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

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

Golf course for the elderly