PN junctions and diodes
What is a common way to make a metal-semiconductor contact ohmic (resistive)?
- AHeavily dope the semiconductor surface at the contact so carriers can tunnel through the barrier easily
- BMake the semiconductor surface at the contact lightly doped
- CInsert a thick oxide between the metal and semiconductor
Show answer and explanation
Answer: A. Heavily dope the semiconductor surface at the contact so carriers can tunnel through the barrier easily
A Schottky barrier forms between a metal and a semiconductor, but heavily doping the semiconductor makes the barrier extremely thin, letting carriers tunnel through it. This gives a low-resistance contact regardless of current direction (an ohmic contact).
- A. Correct. Heavy doping thins the barrier and allows tunneling current.
- B. Light doping makes the barrier thicker and tends to produce a Schottky contact.
- C. A thick insulator makes current flow harder.