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hoes are vacancies left by the electron in the valence band. hence there cannot be holes in the conduction band
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What is the connection between Fermi Level and Electronic Grade Materials?
fermi level:- This is the level of energy that lies in the forbiddan gap. It is the level of energy where the concentration of electrons in conduction band is equal to the concentration of holes in valance band. Since in intrinsic semiconductor the probability of electrons in conduction band is equal to the holes in valance band therefore lies exactly in the middle of fforbiddan gap In case of extrinsic semiconductor material, that depends what sort of dopping is there. If the donar impurity is there, it will shift towards conduction band, and if there is acceptor impurity it will shift towards valance band.
If a pure Si crystal has a million free electrons inside it how many holes does it have.what happens to the no of free electrons and holes if the ambient temperature increases?
If the crystal is pure Si (no dopants or impurities) then the number of free electrons in the conduction band will be equal to the number of holes in the valence band. Each electron leaves behind a hole when it is thermally excited into the conduction band. If the ambient temp. increases, there will be more thermal energy available which will increase both the number electrons and the number of holes.
Is bismuth a semiconductor or conductor?
the band structure of bismath suggests a low density of conduction electrones and holes,so it is semi conductor
Are free electron in valence band or conduction band?
In semiconductors free electrons are in conduction bands.
What is the working principle of semiconductor laser?
The principle of semiconductor laser is very different from CO2 and Nd:YAG lasers. It is based on "Recombination Radiation" The semiconductor materials have valence band V and conduction band C, the energy level of conduction band is Eg (Eg>0) higher than that of valence band. To make things simple, we start our analysis supposing the temperature to be 0 K. It can be proved that the conclusions we draw under 0 K applies to normal temperatures. Under this assumption for nondegenerate semiconductor, initially the conduction band is completely empty and the valence band is completely filled. Now we excite some electrons from valence band to conduction band, after about 1 ps, electrons in the conduction band drop to the lowest unoccupied levels of this band, we name the upper boundary of the electron energy levels in the conduction band the quasi-Fermi level Efc. Meanwhile holes appear in the valence band and electrons near the top of the valence band drop to the lowest energy levels of the unoccupied valence energy levels, leave on the top of the valence band an empty part. We call the new upper boundary energy level of the valence band quasi-Fermi level Efv. When electrons in the conduction band run into the valence band, they will combine with the holes, in the same time they emit photons. This is the recombination radiation. Our task is to make this recombination radiation to lase
What are conduction band?
The quantum mechanical energy band where electrons reside in semiconductors that participate in electrical conduction.
Why conduction band and valence band partially filled?
No. Conduction band is basically the unfilled energy levels into which electrons can be excited to provide conductivity.
Effective density of states in conduction band?
All of the distributed electron states in the conduction band is represented by an effective density of states (NC)
What is the difference between direct and indirect energy?
The band gap represents the minimum energy difference between the top of the valence band and the bottom of the conduction band, However, the top of the valence band and the bottom of the conduction band are not generally at the same value of the electron momentum. In a direct band gap semiconductor, the top of the valence band and the bottom of the conduction band occur at the same value of momentum.In an indirect band gap semiconductor, the maximum energy of the valence band occurs at a different value of momentum to the minimum in the conduction band energy
What are the difference between direct and indirect band gap materials?
In a direct band gap the electron only needs energy to jump to the conduction band. In an indirect band an electron needs energy and momentum to jump to the conduction band
What are conduction?
The quantum mechanical energy band where electrons reside in semiconductors that participate in electrical conduction.
Why is a rubber band an insulator?
The electron configuration of rubber (natural of artificial is such that there is a big gap between valance band and conduction band of electrons. Electrons has to make a transition from valence band to conduction band in order to conduct electricity.
