# material and device ( electrical engineering )

1. Draw the band diagram for p-type silicon with a hole concentration of 1014cm-3. Look up the constants for silicon at room temperature in your books, or online.
2. If the electron concentration in silicon is 1018cm-3, what is the hole concentration?
3. If the Fermi level is in the middle of the bandgap, what is the electron and hole concentration for Silicon at room temperature?
4. If the Fermi level, Ef is 0.3 eV above Ei, what is the electron concentration? What is the hole concentration?
5. Write down an exponential equation for the electron concentration in silicon as a function of Ef position.
6. If the mobility of electrons in my silicon is 1000cm2/Vs, and the electric field across it is 103V/cm, what is the drift velocity of the electrons?
7. Using the electron velocity above, what is the resistivity of Silicon, assuming the electron concentration is 1016cm-3? Compare this with the resistivity of glass, and copper.
8. Explain what drift and diffusion are. How are they related?
9. Explain using a few paragraphs, and some pictures, how a pn diode works. Make sure to include a band diagram, and also explain why current flows only in one direction and not the other.