Physics of Semiconductor Devices

Exam March 2007, Problem 3

In a Schottky contact, the Fermi energy is pinned to the middle of the gap by interface states. The semiconductor is p-doped.

(a) Draw the band diagram indicating the Fermi energy, the valence band, and conduction band.

(b) Explain the difference between a Schottky contact, an ohmic contact, and a tunnel contact.

(c) Why is the Schottky diode formed at the gate of a MESFET usually reverse biased during transistor operation?