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

Lesson 2: Basics of semiconductors

# Minority charge carriers in extrinsic semiconductors

When we add impurities to semiconductors, what happens to minority charge carriers? Do they remain the same? In this video, we will explore what happens to minority charge carriers in an extrinsic (doped) semiconductor. Created by Mahesh Shenoy.

## Want to join the conversation?

• Is it reasonable to assume the generation rate for intrinsic semiconductor and doped semiconductor are the same? For N-type, for example, the electrons in the donor level are much easier to be thermally excited to the conduction band, doesn't that mean higher generation rate?
• try to understand that in extrinsic s.c since it is easier to thermally excite the electron similarly it will be hard to generate holes in simple words generation rate will be same intrinsic and extrinsic s.c at thermal equilibrium b/c in extrensic s.c if n(e)are inc. then n(h) are decreasing with same rate
• I didnt understand one part in the video. For some reason he equated k10^20 = k10^16*n(holes). Why did he do this
• This was explained in his previous video titled Intrinsic Semiconductors
(1 vote)
• Minority charge carriers weren't really discussed in this video as far as I can tell. Or maybe i'm missing something?
(1 vote)
• Well he actually did. But just for N-type. You see he did the math to prove that the number of electons is 10^16 and the number of holes is 10^4 in an N-type semiconductor...which actually proves the fact that there is way less holes in N-type semiconductor and hence holes are minority charge carriers in N-type semiconductors
(1 vote)
• well, are those holes formed by thermal energy, compensated by the electrons of the semiconductor element or by the impurity?
(1 vote)
• The holes, I believe, are still only compensated by the electrons of the semiconductor element. The electrons due to the impurity only contribute to the conduction band of the semiconductor and not the valence bond.
(1 vote)
• Hello dear teacher,
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(1 vote)
• The extra million electrons provided by the P atoms should be included in EITHER:
n(e)=10^(10)+10^(16)≈10^(16)
OR:
n(h)=10^(10)-10^(6)≈10^(10)

The same electrons cannot participate in two different processes simultaneously at thermal equilibrium, right?

Then in the above video, how come do the same electrons increase n(e) and decrease n(h)?
(1 vote)
• Can I say that motion of hole is used to model the electrons that are moving in valence band which is different from the motion of electrons in conduction band?
(1 vote)
• Yes, indeed it's the electrons in the valence band which are moving. A hole is nothing but the absence of an electron.
Good thinking! Keep on learning..
• It is not clear to me, what you are to say through this video, sir. What exactly are minority charge carriers. That term didn't even come up in the entire video.