If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Modern Physics (Essentials) - Class 12th>Unit 5

Lesson 2: Basics of semiconductors

# Extrinsic semiconductors P-type

In this video, we will explore the P-type semiconductors.  Created by Mahesh Shenoy.

## Want to join the conversation?

• How number of holes larger than number of electron , when number of B much less compare to Si and one hole create by one B ?
Where one B + Si = 3+4 electron and only 1 hole .
• From the author:Whenever an electron from Si-Si covalent bond breaks free, we get 1 hole and 1 free electron. But with the introduction of Boron, we are getting holes without any free electrons. This is why the number of holes increases with the addition of B.
• Why should the semi conductor flow charge in on direction?
• watch the videos "The PN junction" and "PN junction biasing"
(1 vote)
• Why electrons jump into acceptor level instead the fact that accepter level lies in the forbidden region?
(1 vote)
• The forbidden region is only for silicon. Boron has its own diagram. the acceptor level is an energi level for boron not silicon.
• So, it is right to say that the holes roam only between Si atoms?

I mean, in order to have a hole created (due to the doping per se, and not due to thermal fluctuations), we need an electron jump to the acceptor's energy level. Which means that all B atoms will have their outer shells complete and holes will exist only in Si atoms (i.e., in the valence band).

Is the above reasoning correct?
• correct if you have the right energi. The Boron`s energi level is a bit higher then the silicon`s valence energi level so you need some kinde of energi to get the electrones to migrat to the borons energi level
• how are P-type & N-type semiconductors made? Explain with the help of diagram the forward and reverse biasing of PN junction?
(1 vote)
• These are made by doping of various trivalent(in P type semiconductors) elements and pentavalent (for n type semiconductors) elements. For further explanation with diagram refer to next lessons on semiconductors
(1 vote)
• No of holes increased in valence band but it is conduction band which is responsible for movement of free charge carriers. so how holes can move in valence band and produce current?
(1 vote)
• To be specific, what is the ratio of Si atoms to B atoms in a typical P-type semiconductor? If it's <=1 why do we care for holes being on the valence band of Si atoms and not volume of overall vacancy in the resulting material?
(1 vote)
• In the p-type semiconductors the holes are created in the Valence Band, not the conduction band. So how do they become better at conducting?
(1 vote)
• P and N-type. what will happen when you have a temperature difference in the semiconductor itself. how will the charges flow?
(1 vote)