Determining Charge Carrier Concentration from Doping in Si Crystal

In summary, the silicon crystal with doping densities of 10^15 cm^-3 of antimony and 10^16 cm^-3 of boron will be type p. The concentration of minority charge carriers will be 10^4 cm^-3 and the concentration of majority charge carriers will be 10^16 cm^-3. This is because boron is an acceptor and Sb is a donor, making the crystal P type. The thermal equilibrium minority carrier density is Npo=ni^2/p0 and the thermal equilibrium density of electrons and holes are n0 and p0, respectively. The electron density in intrinsic semiconductor is represented by ni.
  • #1
415
0
a silicon crystal is doped with 10^15 cm^-3 atoms of antimony
and its also doped with 10^16 cm^-3 atoms of boron

will the crystal be type p or type n

what will be the concentration of minory charge carriers and majority charge carriers
?

Boron has 3 electrons in outer circle
and Sb has 5 on the outer circle
so its type "p" because there there is more +3 then +5
thats as far as could go
how to find the concentration of minory charge carriers and majority charge carriers
 
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  • #2
nhrock3 said:
a silicon crystal is doped with 10^15 cm^-3 atoms of antimony
and its also doped with 10^16 cm^-3 atoms of boron

will the crystal be type p or type n

what will be the concentration of minory charge carriers and majority charge carriers
?

Boron has 3 electrons in outer circle
and Sb has 5 on the outer circle
so its type "p" because there there is more +3 then +5
thats as far as could go
how to find the concentration of minory charge carriers and majority charge carriers

But the two doping densities are not the same...
 
  • #3
boron is an acceptor donates 1 hole per atom.
Sb is a donor, donates 1 electon per atom

10^16 boron atoms vs 10^15 Sb means that this is a P type.

n0p0=ni^2

minority negative charge carriers : Npo=ni^2/p0 = 10^20/10^16 = 10^4 cm^-3

major charge carriers = 10^16
 
  • #4
what are n0 p0 and ni
?

what N represents in Npo=ni^2/p0 ?
 
  • #5
n0 is thermal equibrium density of electrons
p0 is thermal equilibruim density of holes

ni = electron density in intrinsic semiconductor

Npo is the thermal equilibrium minority carrier density.
 
  • #6
how you get that the "major charge carriers = 10^16 "
?
 

1. How do you determine the charge carrier concentration in a Si crystal?

To determine the charge carrier concentration in a Si crystal, one must first measure the conductivity of the crystal at various temperatures. This can be done by passing a small current through the crystal and measuring the resulting voltage. Next, the crystal must be doped with a known amount of impurities, typically either boron or phosphorus. The conductivity must then be measured again at the same temperatures. By comparing the two sets of data, the charge carrier concentration can be calculated using the appropriate equations.

2. What is doping and how does it affect charge carrier concentration?

Doping is the process of intentionally introducing impurities into a semiconductor crystal, such as silicon. These impurities, also known as dopants, can either add or remove electrons from the crystal's structure. This changes the number of free charge carriers in the crystal and thus affects the charge carrier concentration.

3. What are the different types of doping and how do they differ?

The two main types of doping are n-type and p-type. N-type doping involves adding a dopant, such as phosphorus, which adds extra electrons to the crystal's structure. This creates more free electrons, making the crystal a better conductor. P-type doping involves adding a dopant, such as boron, which removes electrons from the crystal's structure. This creates more holes, which can act as positive charge carriers.

4. Can the charge carrier concentration in a Si crystal be controlled?

Yes, the charge carrier concentration in a Si crystal can be controlled by adjusting the amount and type of dopants used. By carefully selecting the type and concentration of dopants, the conductivity and charge carrier concentration of the crystal can be finely tuned to meet the desired specifications for a particular application.

5. Why is determining charge carrier concentration important in semiconductor devices?

The charge carrier concentration is an important parameter in semiconductor devices because it affects the electrical properties of the device. By controlling the charge carrier concentration, the conductivity and other important characteristics of the device can be optimized for its intended purpose. This allows for the production of more efficient and reliable semiconductor devices.

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