Question about semiconductors' holes.

In summary, holes are vacancies left in the valence band after an electron is knocked out, typically present in semiconductors but not in metals during photoelectric effects. The mass of a hole depends on the material and its characteristics are different from electrons, behaving in the opposite direction under an applied field. Holes are both mobile and localized, meaning they are able to move freely but are still associated with an atom or molecule.
  • #1
Freeze3018
22
0
I know holes are made/present after electron leaves its place but are holes present in metals during photo electric effects?

what is the mass of a hole (if it has any)?

what are its characteristics are they exactly opposite of electron ( i mean its behaviour in electric and magnetic field ) ?
 
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  • #2
When calculating the dynamics for a crystal in an applied field, you need to include the contribution from every band. Using a derivation from solid state which I can't quote exactly, you can show that you can solve for the motion by considering the evolution of the occupied states (the electrons), or equivalently, the unoccupied states (the holes). You choose one convention for each band because otherwise you would be counting twice. Conceptually, the holes are only useful in the valence band where almost all states are occupied. But if you wanted to, you could treat the conduction band as a huge number of holes as well.

In the normal usage, holes are in the valence band and electrons are in the conduction band. Their properties depend on the band structure, and in general, will not be exact opposites of each other. Electrons and holes can have very different effective masses in some materials.
 
  • #3
Freeze3018 said:
I know holes are made/present after electron leaves its place but are holes present in metals during photo electric effects?

what is the mass of a hole (if it has any)?

Gravitational or inertial?
 
  • #4
Freeze3018 said:
I know holes are made/present after electron leaves its place but are holes present in metals during photo electric effects?

A "Hole" typically refers to a vacancy left in the valence band that is mobile yet localized, so that it acts as an effective positively charged object free to move around and carry current. If the photon in the photoelectric effect knocks an electron out of the valence band (typical in semiconductors), then, yes, it will leave a hole. This effect is used in photodiodes. If the photon knocks a conduction electron (as is abundant in metals) out of the material, it does not leaves a hole, because the vacancy it leaves behind is not localized and does not act as a pseudo-particle.

Freeze3018 said:
what is the mass of a hole (if it has any)?

It depends on the material. The hole is assigned an effective mass based on how it moves about under forces, which differs by material. For instance, Silicon has a heavy hole effective mass of 49% the mass of a totally free electron.

Freeze3018 said:
what are its characteristics are they exactly opposite of electron ( i mean its behaviour in electric and magnetic field ) ?

Holes are positively charged and have different masses than electrons. This means they will flow the opposite direction as electrons under an applied field.
 
  • #5
THnax chrisbaird but what do u mean by "mobile yet localized"
 
  • #6
Localization means that an electron/hole is associated with an atom/molecule. Don't quite get what is mobile + localized.
 

FAQ: Question about semiconductors' holes.

What are holes in semiconductors?

Holes in semiconductors are essentially the absence of an electron in the valence band. They behave as positively charged particles and can move through the material similarly to electrons.

How do holes contribute to the conductivity of semiconductors?

Holes can contribute to the conductivity of semiconductors by allowing for the movement of charge through the material. When an electron moves from one atom to another, it leaves behind a hole which can then be filled by another electron, creating a chain reaction that allows for the flow of current.

What is the difference between holes and electrons in semiconductors?

The main difference between holes and electrons in semiconductors is their charge. Electrons carry a negative charge while holes carry a positive charge. Additionally, electrons are present in the conduction band while holes are present in the valence band.

How are holes created in semiconductors?

Holes can be created in semiconductors through a process called doping. This involves adding impurities to the material, either by introducing atoms with fewer electrons than the semiconductor (p-type doping) or by introducing atoms with more electrons (n-type doping).

Can holes be physically observed in semiconductors?

Holes themselves cannot be physically observed in semiconductors. However, their effects on the movement of charge can be observed through various experiments and measurements.

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