Density of carriers in a Conduction band

In summary, the task is to find the density of carriers in the conduction band of intrinsic silicon at room temperature using the given equations and values. The Fermi Dirac probability function is used to calculate the integral, but there is some uncertainty about the correct values to use for the probability function. The final calculated density value is 2.07276*10^18 m^-3, which is different from the expected 1.102*10^16 m^-3. Further clarification and guidance is needed to determine the error in the calculations.
  • #1
cybhunter
25
0

Homework Statement



Find the density of carriers N in the conduction band of intrinsic silicon at room temperature




Homework Equations




lower integrand Ec, upper integrand= Ec+1*qe,

Eg=1.12eV,
Ev=0
Ec=Ev+Eg
Ef=Ev+Eg/2

m*n=1.08*(9.11*10^31),
T=300K,
kb=1.38065*10^-23J/K ,
h=(6.625*10^-34)


fF(E)=1/(1+e^((E-Ef)/(kT))
g(E)=4*pi*(2*m*n)^(3/2)/h^3*(E-Ec)^(1/2)


N=integral(Ff(E)*g(E))dE

The Attempt at a Solution



for fF(E): 1/(1+e^(0.56/0.0259)= 4.07239*10^-10

for g(E): 4*pi*(2*m*n)^(3/2)/h^3*(E-Ec)^(1/2)= 1.159*10^56*(E-Ec)^(1/2)

intergating from Ec to Ec+1*qe: 3.23869*10^46*[Ec+1*qe-Ec]

converting the eV values to Joules, and simplifying the interrogation: 3.23869*10^46*[1.6*10^-19]

the value I got is 2.07276*10^18 m^-3


The value I should have received is 1.102*10^16 m^-3

in the process of solving for the density function, I symbolical replaced E-Ec with a delta E and integrated to get 2/3*(E-Ef)^(3/2), and took to the limits between Ec and Ec+1*qe, effectively leaving a difference of 1*qe. Solving just for the density I have no problem. The trouble I'm having lies with the Fermi Dirac probability function.

When solving for the Fermi Dirac, I found online (Microelectronics I: Introduction to the quantum Theory of Solids): e^(Ec-(Ec-Ef))/kT. Since I was given Ef as Eg/2 (0.56eV), I end up getting a value for the probability function of 4.07239*10^-10, which apparently is wrong.


What am I doing wrong?
 
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  • #2
Did I use the wrong values when solving for the Fermi Dirac probability function? Is it possible that the text is incorrect?
 

1. What is the conduction band?

The conduction band is the energy level in a material where electrons are free to move and conduct electricity.

2. How is the density of carriers in the conduction band determined?

The density of carriers in the conduction band is determined by the number of electrons that are available to move into the conduction band, which is influenced by factors such as temperature and impurities in the material.

3. What is the relationship between the density of carriers in the conduction band and electrical conductivity?

The density of carriers in the conduction band is directly proportional to the electrical conductivity of a material. This means that as the density of carriers increases, the material becomes more conductive.

4. How does the density of carriers in the conduction band change with temperature?

The density of carriers in the conduction band typically increases with temperature, as more electrons are able to gain enough energy to move into the conduction band and contribute to electrical conductivity.

5. What factors can affect the density of carriers in the conduction band?

The density of carriers in the conduction band can be affected by factors such as temperature, impurities in the material, and the presence of electric fields or magnetic fields.

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