Minority charge carriers - what are these?

In summary, the conversation revolves around the concept of minority charge carriers in semiconductors. The person asking the question is confused about why holes are considered minority carriers in an N-type semiconductor, as they believe there is always a one-to-one correspondence between electrons and holes. Another person explains that the minority/majority carriers refer to the free charges, not the charges on any ions in the lattice. They clarify that in an n-type doped material, the hole left behind after a donor atom donates an electron to the conduction band is localized to the donor atom, making it a minority carrier. This differs from when a valence band electron is excited into the conduction band, as the hole in this case is also free.
  • #1
Kenny_L
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Hi all, this question comes from an old related thread .. https://www.physicsforums.com/threads/help-in-semiconductors-minority-and-majority-carriers.613598/

I'm also interested in the definition of these 'minority charge carriers' in semiconductors.

I don't understand the explanations in the old thread.

The way I've been seeing it is... take an N-type semiconductor for example, which has impurity atoms introduced (to say a Silicon lattice) so that a donor impurity atom will have 1 extra electron than a silicon atom. However, that extra 1 electron is accounted for (neutralised) because the donor impurity atom is neutral to begin with. So even if that electron becomes 'free', then there will be a free hole to go with it. So that's a one-to-one correspondence. So the free hole won't be a 'minority' in that case (since the hole concentration still equals electron concentration in terms of 'free' carriers).

Then, somebody indicates that temperature (thermal energy) is able to break covalent bonds, resulting in an electron-hole pair. And they say that this generates minority carriers (ie. holes being minority carriers). However, my view is that when covalent bonds are broken due to temperature, there's still going to be one free electron to every free hole, right? So this means that the holes are never going to be in the 'minority', right?

Can someone help to set things straight - to explain why holes are 'minority' carriers in N-type semiconductors? The way I see it right now is... holes don't seem to be in the minority if there's always going to be one-to-one correspondence between electrons and holes. There also doesn't appear to be any diagrams in books etc that actually show clearly how (for example) the holes actually become a 'minority'. Thanks for your help in advance!
 
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  • #2
Kenny_L said:
Hi all, this question comes from an old related thread .. https://www.physicsforums.com/threads/help-in-semiconductors-minority-and-majority-carriers.613598/

I'm also interested in the definition of these 'minority charge carriers' in semiconductors.

I don't understand the explanations in the old thread.

The way I've been seeing it is... take an N-type semiconductor for example, which has impurity atoms introduced (to say a Silicon lattice) so that a donor impurity atom will have 1 extra electron than a silicon atom. However, that extra 1 electron is accounted for (neutralised) because the donor impurity atom is neutral to begin with. So even if that electron becomes 'free', then there will be a free hole to go with it. So that's a one-to-one correspondence. So the free hole won't be a 'minority' in that case (since the hole concentration still equals electron concentration in terms of 'free' carriers).

Then, somebody indicates that temperature (thermal energy) is able to break covalent bonds, resulting in an electron-hole pair. And they say that this generates minority carriers (ie. holes being minority carriers). However, my view is that when covalent bonds are broken due to temperature, there's still going to be one free electron to every free hole, right? So this means that the holes are never going to be in the 'minority', right?

Can someone help to set things straight - to explain why holes are 'minority' carriers in N-type semiconductors? The way I see it right now is... holes don't seem to be in the minority if there's always going to be one-to-one correspondence between electrons and holes. There also doesn't appear to be any diagrams in books etc that actually show clearly how (for example) the holes actually become a 'minority'. Thanks for your help in advance!
The minority/majority carriers refer to the free charges, not the charges on any ions in the lattice. I.e. in an n-type doped material, the donor donates an electron to the conduction band, where the electron is then delocalised, in contrast the hole left behind is localised to the donor atom. This differs to when a valence band electron is excited into the conduction band, as in this case the hole is also free due to being part of the band rather than associated with a particular atom.
 
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Likes Kenny_L
  • #3
Vagn said:
The minority/majority carriers refer to the free charges, not the charges on any ions in the lattice. I.e. in an n-type doped material, the donor donates an electron to the conduction band, where the electron is then delocalised, in contrast the hole left behind is localised to the donor atom. This differs to when a valence band electron is excited into the conduction band, as in this case the hole is also free due to being part of the band rather than associated with a particular atom.

Hi Vagn! Thanks so much - actually, incredibly much - for your comments about this. I had always been trying to understand this kind of thing. Thanks for helping me to understand the concept of minority charge carriers. Greatly appreciated!
 

Related to Minority charge carriers - what are these?

1. What are minority charge carriers?

Minority charge carriers are particles that have an opposite charge to the majority charge carriers in a material. They exist in small numbers compared to the majority carriers and play a crucial role in the movement of electric current in semiconductors.

2. What types of minority charge carriers are there?

The two main types of minority charge carriers are electrons and holes. Electrons are the minority carriers in p-type semiconductors, while holes are the minority carriers in n-type semiconductors.

3. How do minority charge carriers affect the conductivity of a material?

Minority charge carriers can either increase or decrease the conductivity of a material, depending on the type of semiconductor and the presence of impurities. In p-type semiconductors, minority carriers (electrons) are attracted to the positively charged holes, increasing conductivity. In n-type semiconductors, minority carriers (holes) are repelled by the negatively charged electrons, decreasing conductivity.

4. What causes the generation of minority charge carriers?

Minority charge carriers are generated through the process of doping, where impurities are intentionally added to a semiconductor material. This creates extra electrons or holes, which serve as minority carriers and contribute to the electrical properties of the material.

5. How do minority charge carriers affect the performance of electronic devices?

The presence of minority charge carriers in a semiconductor material is necessary for the function of many electronic devices, such as transistors and diodes. They allow for the control and manipulation of electric current, which is essential for the operation of these devices.

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