3 Improved formatting and corrected the incorrectly copied the numerical values from the textbook example
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I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $10^{13}$ cm$^{-3}$$10^{13}\ \mathrm{cm}^{-3}$ per $\mu s$$\mu$s in a sample of Siliconsilicon.

The equilibrium concentration of electrons in the sample is $n_0 = 10^{14}$ cm$^{-3}$$n_0 = 10^{14}\ \mathrm{cm}^{-3}$.

Also, it gives $\tau_n = \tau_p = 2\,\mu s$$\tau_n = \tau_p = 2\ \mu\mathrm{s}$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n = 2.0 \times 10^{14}$ ($n_0 = 1.0 \times 10^{14}$)

$p = 2.0 \times 10^{14}$ ($p_0 = 2.25 \times 10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i = 0.233$ eV$F_n-E_i = 0.233\ \mathrm{eV}$

$E_i-F_p = 0.186$ eV$E_i-F_p = 0.186\ \mathrm{eV}$

The equilibrium fermi level ($E_F)$$E_F$) being at $E_F-E_i=0.228$ eV $E_F-E_i=0.228\ \mathrm{eV}$

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $10^{13}$ cm$^{-3}$ per $\mu s$ in a sample of Silicon.

The equilibrium concentration of electrons in the sample is $n_0 = 10^{14}$ cm$^{-3}$.

Also, it gives $\tau_n = \tau_p = 2\,\mu s$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n = 2.0 \times 10^{14}$ ($n_0 = 1.0 \times 10^{14}$)

$p = 2.0 \times 10^{14}$ ($p_0 = 2.25 \times 10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i = 0.233$ eV

$E_i-F_p = 0.186$ eV

The equilibrium fermi level ($E_F)$ being at $E_F-E_i=0.228$ eV

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $10^{13}\ \mathrm{cm}^{-3}$ per $\mu$s in a sample of silicon.

The equilibrium concentration of electrons in the sample is $n_0 = 10^{14}\ \mathrm{cm}^{-3}$.

Also, it gives $\tau_n = \tau_p = 2\ \mu\mathrm{s}$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n = 2.0 \times 10^{14}$ ($n_0 = 1.0 \times 10^{14}$)

$p = 2.0 \times 10^{14}$ ($p_0 = 2.25 \times 10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i = 0.233\ \mathrm{eV}$

$E_i-F_p = 0.186\ \mathrm{eV}$

The equilibrium fermi level ($E_F$) being at $E_F-E_i=0.228\ \mathrm{eV}$

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?
2 Improved formatting and corrected the incorrectly copied the numerical values from the textbook example
source | link

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $2*10^{13} cm^{-3}$$10^{13}$ cm$^{-3}$ per $\mu S$$\mu s$ in a sample of $Si$Silicon.

The equilibrium concentration of electrons in the sample is $n_0=10^{14}cm^{-3}$$n_0 = 10^{14}$ cm$^{-3}$.

Also, it gives $\tau_n=\tau_p=2\mu S$$\tau_n = \tau_p = 2\,\mu s$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n=1.2*10^{14}$$n = 2.0 \times 10^{14}$ ($n_0=1.0*10^{14}$$n_0 = 1.0 \times 10^{14}$)

$p = 2.0*10^{14}$$p = 2.0 \times 10^{14}$ ($p_0=2.25*10^6$$p_0 = 2.25 \times 10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i=0.233eV$$F_n-E_i = 0.233$ eV

$E_i-F_p=0.186eV$ $E_i-F_p = 0.186$ eV

The equilibrium fermi level ($E_f)$$E_F)$ being at $E_f-E_i=0.228eV$$E_F-E_i=0.228$ eV

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $2*10^{13} cm^{-3}$ per $\mu S$ in a sample of $Si$.

The equilibrium concentration of electrons in the sample is $n_0=10^{14}cm^{-3}$.

Also, it gives $\tau_n=\tau_p=2\mu S$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n=1.2*10^{14}$ ($n_0=1.0*10^{14}$)

$p = 2.0*10^{14}$ ($p_0=2.25*10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i=0.233eV$

$E_i-F_p=0.186eV$

The equilibrium fermi level ($E_f)$ being at $E_f-E_i=0.228eV$

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $10^{13}$ cm$^{-3}$ per $\mu s$ in a sample of Silicon.

The equilibrium concentration of electrons in the sample is $n_0 = 10^{14}$ cm$^{-3}$.

Also, it gives $\tau_n = \tau_p = 2\,\mu s$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n = 2.0 \times 10^{14}$ ($n_0 = 1.0 \times 10^{14}$)

$p = 2.0 \times 10^{14}$ ($p_0 = 2.25 \times 10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i = 0.233$ eV

$E_i-F_p = 0.186$ eV

The equilibrium fermi level ($E_F)$ being at $E_F-E_i=0.228$ eV

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?
1
source | link

Why are there two quasi Fermi levels and only one Equilibrium Fermi level?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels.

For example,

A steady state of Electron Hole pairs are created at the rate of $2*10^{13} cm^{-3}$ per $\mu S$ in a sample of $Si$.

The equilibrium concentration of electrons in the sample is $n_0=10^{14}cm^{-3}$.

Also, it gives $\tau_n=\tau_p=2\mu S$. I am not sure what this is but I think this is the average recombination time.

The result is that the new levels of carrier concentrations (under the described steady state) are

$n=1.2*10^{14}$ ($n_0=1.0*10^{14}$)

$p = 2.0*10^{14}$ ($p_0=2.25*10^6$)

I follow until here but I get a bit confused after this.

The book goes onto say that this results in two different virtual Fermi levels which are at:

$F_n-E_i=0.233eV$

$E_i-F_p=0.186eV$

The equilibrium fermi level ($E_f)$ being at $E_f-E_i=0.228eV$

My question:

  1. Why are there two different quasi fermi levels now created?
  2. Why do we not consider two different ones at equilibrium conditions?
  3. Why is it that due to a steady state input of electron hole pairs that we now consider two quasi Fermi levels?
  4. What is the relevance of these new quasi fermi levels?