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प्रश्न
Write two characteristic features to distinguish between n-type and p-type semiconductors ?
उत्तर
In n-type semiconductor, the semiconductor is doped with pentavalent impurity. In it the electrons are majority carriers and holes are minority carrier or ne >> nh [ne − number density of electrons, nh − number density of holes]
In energy band diagram of n-type semiconductor the donor energy level ED is slightly below the bottom of EC conduction band and thus the electron can move to conduction band thus the electron can move to conduction band with even small supply of energy,
In p-type semiconductor, the semiconductor is doped with trivalent impurity. In this the holes are the majority carries and electrons are the minority carriers i.e nh >> ne
In energy-band diagram of p-type, the accepter energy level in slightly above the top of valence band EV.
Thus even with small supply of energy electron from valence band can jump to level EA and ionize the acceptor negatively.
संबंधित प्रश्न
Draw energy band diagrams of an n-type and p-type semiconductor at temperature T > 0 K. Mark the donor and acceptor energy levels with their energies.
The conduction band of a solid is partially filled at 0 K. Will it be a conductor, a semiconductor or an insulator?
In semiconductors, thermal collisions are responsible for taking a valence electron to the conduction band. Why does the number of conduction electrons not go on increasing with time as thermal collisions continuously take place?
When an electron goes from the valence band to the conduction band in silicon, its energy is increased by 1.1 eV. The average energy exchanged in a thermal collision is of the order of kT which is only 0.026 eV at room temperature. How is a thermal collision able to take some to the electrons from the valence band to the conduction band?
Indium antimonide has a band gap of 0.23 eV between the valence and the conduction band. Find the temperature at which kT equals the band gap.
The band gap between the valence and the conduction bands in zinc oxide (ZnO) is 3.2 eV. Suppose an electron in the conduction band combines with a hole in the valence band and the excess energy is released in the form of electromagnetic radiation. Find the maximum wavelength that can be emitted in this process.
The conductivity of an intrinsic semiconductor depends on temperature as σ = σ0e−ΔE/2kT, where σ0 is a constant. Find the temperature at which the conductivity of an intrinsic germanium semiconductor will be double of its value at T = 300 K. Assume that the gap for germanium is 0.650 eV and remains constant as the temperature is increased.
(Use Planck constant h = 4.14 × 10-15 eV-s, Boltzmann constant k = 8·62 × 10-5 eV/K.)
What is forbidden band?
Hydrogen atom in n = 3 state has a lifetime of 10-10 sec. The number of revolutions an electron makes in the n = 3 state before returning to the ground state is ______.
Useful data
`1/(4pi∈_0) = 8.99 xx 10^-34`N m2 C-2; e = 1.60 10-19 C; h = 6.63 10-34 Js; me = 9 × 10-3 kg
Two radioactive substances A and B have decay constants 3λ and λ respectively. At t = 0 they have the same number of nuclei. The ratio of the number of nuclei of A to those of B will be `1/"e"` after a time interval:
