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प्रश्न
The number of silicon atoms per m3 is 5 × 1028. This is doped simultaneously with 5 × 1022 atoms per m3 of Arsenic and 5 × 1020 per m3 atoms of Indium. Calculate the number of electrons and holes. Given that ni= 1.5 × 1016 m−3. Is the material n-type or p-type?
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उत्तर
Number of silicon atoms, N = 5 × 1028 atoms/m3
Number of arsenic atoms, nAs = 5 × 1022 atoms/m3
Number of indium atoms, nIn = 5 × 1020 atoms/m3
Number of thermally-generated electrons, ni = 1.5 × 1016 electrons/m3
Number of electrons, ne = 5 × 1022 − 1.5 × 1016 ≈ 4.99 × 1022
Number of holes = nh
In thermal equilibrium, the concentrations of electrons and holes in a semiconductor are related as:
nenh = ni2
`therefore "n"_"h" = ("n"_"i"^2)/"n"_"e"`
`= (1.5 xx 10^16)^2/(4.99 xx 10^22) ~~ 4.51 xx 10^9`
Therefore, the number of electrons is approximately 4.99 × 1022 and the number of holes is about 4.51 × 109. Since the number of electrons is more than the number of holes, the material is an n-type semiconductor.
संबंधित प्रश्न
Distinguish between 'intrinsic' and 'extrinsic' semiconductors
In a p-type semiconductos, which of the following statement is true:
Distinguish between intrinsic and extrinsic semiconductor. (Give any two points).
Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added. The correct statement is ____________.
A donor impurity results in ______.
Semiconductors formed by doping germanium (Ge) with aluminium (Z = 13) and antimony (Z = 51) are ______.
In n-type semiconductor, the fifth electron ______.
The electron and hole concentration in a semiconductor in thermal equilibrium is given by ______.
In a pure semiconductor crystal of Si, if antimony is added then what type of extrinsic semiconductor is obtained. Draw the energy band diagram of this extrinsic semiconductor so formed.
The conductivity of a semiconductor increases with increase in temperature because ______.
Suppose a ‘n’-type wafer is created by doping Si crystal having 5 × 1028 atoms/m3 with 1 ppm concentration of As. On the surface 200 ppm Boron is added to create ‘P’ region in this wafer. Considering n i = 1.5 × 1016 m–3, (i) Calculate the densities of the charge carriers in the n and p regions. (ii) Comment which charge carriers would contribute largely for the reverse saturation current when diode is reverse biased.
Two crystals C1 and C2, made of pure silicon, are doped with arsenic and aluminium respectively.
Identify the extrinsic semiconductors so formed.
In an extrinsic semiconductor, the number density of holes is 4 × 1020 m-3. If the number density of intrinsic carriers is 1.2 × 1015 m-3, the number density of electrons in it is ______.
Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of ______.
- Assertion (A): Putting the p-type semiconductor slab directly in physical contact with the n-type semiconductor slab cannot form the pn junction.
- Reason (R): The roughness at contact will be much more than inter atomic crystal spacing and continuous flow of charge carriers is not possible.
The majority charge carriers in a P-type semiconductor are ______.
