Problem 1
(a) How does a Zener diode work? Draw a band diagram (conduction band, valence band, fermi energy).

(b) How do you make a Zener diode? Explain how the two sides of the diode are doped and why.

(c) What is a Zener diode used for?

(d) What is avalanche breakdown?

Problem 1
(a) Draw the band diagram (valence band, conduction band, Fermi energy) for a Schottky diode with a $n$ doped semiconductor at zero bias. Assume that interface states pin the Fermi energy to the middle of the semiconducting gap at the interface.

(b) Draw the band diagram in forward bias. Of the current transport mechanisms we discussed in course (drift, diffusion, thermionic emission, and tunneling) which are dominant in a forward biased Schottky diode. Which are dominant in a reverse biased diode?

Problem 3
(a) Draw an n-channel JFET.

(b) Explain how a JFET works.

(c) The gate of an n-channel JFET is forward biased and minority holes are injected into the channel where they diffuse to the n+ drain. What happens to the holes there?

Problem 4
(a) Describe how a solar cell works.

(b) The depletion region of a solar cell has a certain thickness in the dark. What determines this thickness? What happens to the depletion width when light falls on the solar cell?

(c) What limits the efficiency of a solar cell?