Fermi level change in semiconductors

In summary, the acceptor level of a semiconductor does depend on the type of base used, as it is a product of both the crystal structure and interatomic spacing. The band gap for Silicon is twice that of Germanium, so the acceptor level would be different if all Si atoms were replaced with Ge atoms. There is no general rule for predicting the exact change in the acceptor level, as it can vary depending on the specific compound semiconductor. However, a 2003 paper showed that there is a universal energy level for hydrogen in semiconductors aligned with a unified scale.
  • #1
Helena Wells
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TL;DR Summary
Does the acceptor level or donor level change if we change the base of the semiconductor?
Suppose we have a crystal lattice of doped Si with dopant Boron atoms. The energy level of the holes of the Boron atoms are just some eV above the valence band of Si.

My question: If we replace all the Si atoms with Ge atoms will the acceptor level change or not? I don't think it will change but why not ask it? In other words, does the acceptor level depend on the type of semiconductor we use as base?
 
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  • #2
The band structure is a product of the crystal structure (which reflects the structure of the base) as well as the interatomic spacing. The band gap for Silicon is twice that of Germanium and so yes it does depend. I believe the most important effect is the interatomic distance, but don't quote me..
 
  • #3
So will it be higher or lower?Is there a general rule for it?
 
  • #4
hutchphd said:
The band structure is a product of the crystal structure (which reflects the structure of the base) as well as the interatomic spacing. The band gap for Silicon is twice that of Germanium and so yes it does depend. I believe the most important effect is the interatomic distance, but don't quote me..
@hutchphd what are you studying/have you studied?
 
  • #5
Long ago I did solid state theory...mostly surfaces and scattering from surfaces. I am now retired after doing optical, electronic, and systems design mostly for medical devices for 25 years . Also folks would occasionally hire me just for another novel look at a problem. I am a better engineer than I am a physicist...but I do love knowing the physics.
 
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  • #6
Helena Wells said:
So will it be higher or lower?Is there a general rule for it?

I do not believe there is a general rule of thumb. Especially in complex compund semiconductors (like oxides and nitrides).
However in 2003, it was shown that hydrogen has a universal energy level provided that the band gap of the semiconductor is aligned according to unified scale (for example aligned with respect to vacuum level).

This is the paper that pointed this out:
https://www.nature.com/articles/nature01665
 
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FAQ: Fermi level change in semiconductors

1. What is the Fermi level in semiconductors?

The Fermi level is the highest energy level in a semiconductor material that is occupied by electrons at 0 Kelvin, or absolute zero temperature. It represents the energy level at which there is a 50% probability of finding an electron.

2. How does the Fermi level change in semiconductors?

The Fermi level in semiconductors can change due to a variety of factors such as temperature, doping, and external electric fields. It can either shift up or down depending on the type of semiconductor and the specific conditions.

3. What is the significance of Fermi level change in semiconductors?

The Fermi level change in semiconductors plays a crucial role in determining the electrical and optical properties of the material. It affects the conductivity, carrier concentration, and bandgap of the semiconductor, which are essential for its functionality in electronic devices.

4. How is the Fermi level change measured in semiconductors?

The Fermi level change in semiconductors can be measured using techniques such as Hall effect measurements, capacitance-voltage measurements, and optical absorption spectroscopy. These methods provide information about the position and magnitude of the Fermi level in the material.

5. Can the Fermi level change be controlled in semiconductors?

Yes, the Fermi level change in semiconductors can be controlled through various means such as doping, temperature, and external electric fields. This allows for the manipulation of the material's electrical and optical properties, making it possible to design and optimize semiconductor devices for specific applications.

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