Question

(4) Which of the following cannot form a near-ohmic contact? (   )

(A) p-n junction

(B) n-n+ junction

(C) p-p+ junction

(D) Semiconductor-metal junction

Answer 1

A. p-n junction

Option A (p-n junction) is the correct answer

Explanation:

What is ohmic contact?

When a metal is connected to semiconductor material , it creates a junction called ohmic contact.

It is a low resistance junction in which current conduction takes place from metal to semi conductor and semiconductor to metal in both ways.

By heavily doping p and n layer p+ and n+ layers formed respectively .

p+ and n+ layers are itself much conducting so when p+ and p combinedp- p+ junction formed which is similar to metal to semiconductor combination.

In the same manner n- n+ junction too,

So p-p+ and n-n+ junction are ohmic contacts

And semiconductor to metal junction is ohmic contact.

p-n junction have barrier potential it cannot form ohmic contact.

Therefore option( A) p-n junction cannot form ohmic contact