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Do semiconductor material have a very high resistance at room temperature?
No. As temperature increases, resistance of semiconductors decrease. This is because semiconductors have a small energy gap between their valence band and conduction band (in the order of 1 eV). Electrons must exist in the conduction band in order for the material to conduct but electrons exist in the valence band naturally. The electrons gain thermal energy for surroundings and jumps the energy gap from valence band to conduction band and hence, the SC material more readily conducts. As temperature increases, electrons can gain more thermal energy, more electrons can enter the conduction band and hence, resistance decreases.
What happens when electrons in conduction band loses its energy and falls to a hole in the valence band?
The energy leaves as either a photon or phonon.
What is the gap between valance band and conduction band in a semi conductor?
Conduction band - The unfilled energy levels into which electrons can be excited to provide conductivity.Valence band - The energy levels filled by electrons in their lowest energy states.
What is the difference between the resistance of conductor and insulator?
Conductors allow most, if not all, electricity to pass through it. This is due to "wandering electrons" that aren't tightly bound to the nucleus of the conductor itself.Resistors conduct some, but not all electricity to pass. It somewhat resists it, hence resistors.Insulators do not allow electricity to pass through it due to the electrons being so tightly bound to the nucleus.
How does doping alter the atomic structure of silicon?
It does not alter the atomic structure of the silicon at all, what it alters is the balance of bulk valence band and conduction band electrons in the crystal of silicon thus altering its bulk conductivity.
What is valence band?
It is the band of energy of an electron in outer most orbit
Are free electron in valence band or conduction band?
In semiconductors free electrons are in conduction bands.
Possibility of holes in conduction band?
hoes are vacancies left by the electron in the valence band. hence there cannot be holes in the conduction band
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
Why semiconductive materials do not conduct current well?
Semiconductive materials do not conduct current well because their valence band is mostly filled and their conduction band is mostly empty, requiring an input of energy for electrons to move from the valence to the conduction band and thus carry a current. Additionally, semiconductors have a wider band gap compared to conductors, which further restricts the flow of electrons.
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 is the relationship between the valence and conduction bands in semiconductor materials?
In semiconductor materials, the valence band is the highest energy band occupied by electrons, while the conduction band is the next higher energy band that electrons can move into to conduct electricity. The energy gap between the valence and conduction bands determines the conductivity of the semiconductor.
What is the difference between the valence band and the conduction band in a material's electronic structure?
The valence band is the energy band in a material where electrons are normally found, while the conduction band is the energy band where electrons can move freely to conduct electricity. The key difference is that electrons in the valence band are tightly bound to atoms, while electrons in the conduction band are free to move and carry electric current.
What is the name of two energy bands at which current is produced in silicon?
The two energy bands in which current is produced in silicon are the valence band and the conduction band. Electrons in the valence band can be excited to the conduction band by absorbing energy, allowing them to move and create an electric current.
Why in intrinsic semiconductors do you need to apply very high potential to transfer electrons from the valence band to the conduction band?
Semiconductors, in the absence of applied electric fields, act a lot like insulators. In these materials, the conduction band and the valence band do not overlap. That's why they insulate. And that's why you have to apply some serious voltage to them to shove the valence electrons across the gap between the valence and conduction bands of these semiconductor materials. Remember that in insulators, there is a "band gap" between the lowest Fermi energy level necessary to support conduction and the highest Fermi energy level of the valence electrons. Same with the semi's. In metals, the conduction band overlaps the valence band Fermi energy levels. Zap! Conductivity.
What is the working principle of Light Emitting Diode and their commercial types?
when electron is excited from valence band to conduction band
Why are Monovalent metal so conductive?
The single valence band electron can easily escape and become a conduction band electron.
