Fermi Level of intrinsic and extrinsic semiconductor

In summary, it is important to understand the limitations and assumptions of equations and not make broad conclusions based on simplified versions of them.
  • #1
kidsasd987
143
4
eq2_6_13.gif
(1)

eq2_6_16.gif
(2)
eq2_6_21.gif
(3)
eq2_6_15.gif
(4)

eq2_6_24.gif
(5)

we can find Equation (5) by dividing po by n0, and write an equation with respect to Ei.
However since equation (3) is a special form of (1) and (2), [when Ef=Ei] we can obtain equation (5) from
any arbitrary Ef.

However, since eq (5) consists of constants only, it will give a result Ef=Ei which contradicts to eq(4).
I know I am wrong, but from which step did I get this wrong?
 
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  • #2


I would like to address this issue and clarify the steps that may have led to this incorrect conclusion.

Firstly, it is important to note that equations (1) and (2) are general equations that describe the relationship between energy (E) and frequency (f). These equations take into account all the variables that affect the energy of a system, such as Planck's constant (h) and the speed of light (c).

Equation (3), on the other hand, is a special case of equations (1) and (2) where the final energy (Ef) is equal to the initial energy (Ei). This means that there is no change in energy and therefore the frequency remains constant.

When we divide po by n0, we are essentially canceling out the variables and simplifying the equation. This does not mean that equation (5) is a special case of equations (1) and (2). In fact, equation (5) is derived from equations (1) and (2) by setting Ef equal to Ei and simplifying the equation.

However, it is incorrect to assume that equation (5) will always give a result of Ef=Ei. This is because equation (5) only considers the constants and does not take into account other variables such as the energy levels of the system. Therefore, when we substitute the values of the constants into equation (5), it may give a result of Ef=Ei, but this does not mean that this will always be the case.

In conclusion, the mistake was made when assuming that equation (5) will always give a result of Ef=Ei. This is not always true and it is important to take into account all the variables and their effects on the system when using equations (1) and (2).
 

What is the Fermi Level of an intrinsic semiconductor?

The Fermi Level of an intrinsic semiconductor is the energy level at which there is an equal probability of finding an electron or hole. In other words, it is the energy level at which the number of electrons in the conduction band is equal to the number of holes in the valence band. This energy level is typically located near the middle of the band gap.

How does the Fermi Level change in an extrinsic semiconductor?

In an extrinsic semiconductor, the Fermi Level is affected by the presence of impurities. When a dopant is added to the semiconductor, it introduces either extra electrons (n-type) or holes (p-type). This changes the balance of electrons and holes in the material, causing the Fermi Level to shift towards the conduction band for n-type and towards the valence band for p-type.

Why is the Fermi Level important in semiconductor devices?

The Fermi Level is important in semiconductor devices because it determines the conductivity of the material. In an intrinsic semiconductor, the Fermi Level is located near the middle of the band gap, making the material a poor conductor. However, in extrinsic semiconductors, the Fermi Level can be manipulated through doping to increase the conductivity of the material, making it useful for electronic devices.

Can the Fermi Level be controlled in semiconductors?

Yes, the Fermi Level can be controlled in semiconductors through the process of doping. By adding impurities to the material, the balance of electrons and holes can be shifted, causing the Fermi Level to move towards the conduction or valence band. This allows for the manipulation of the material's electrical properties, making it a crucial aspect of semiconductor device design.

How does temperature affect the Fermi Level in semiconductors?

As temperature increases, the Fermi Level in semiconductors also shifts. This is due to the fact that temperature affects the number of electrons in the conduction band and holes in the valence band. At higher temperatures, more electrons are promoted to the conduction band, causing the Fermi Level to move towards the conduction band. Conversely, at lower temperatures, more holes are available in the valence band, causing the Fermi Level to move towards the valence band.

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