Class 12 Physics - Chapter Semiconductor Electronics NCERT Solutions | The number of silicon atoms per m 3 is 5
The number of silicon atoms per m 3 is 5 × 10 28 . This is doped simultaneously with 5 × 10 22 atoms per m 3 of Arsenic and 5 × 10 20 per m 3 atoms of Indium. Calculate the number of electrons and holes. Given that n i = 1.5 × 10 16 m −3 . Is the material n-type or p-type?
Number of silicon atoms, N = 5 × 10 28 atoms/m 3
Number of arsenic atoms, n As = 5 × 10 22 atoms/m 3
Number of indium atoms, n In = 5 × 10 20 atoms/m 3
Number of thermally-generated electrons, n i = 1.5 × 10 16 electrons/m 3
Number of electrons, n e = 5 × 10 22 − 1.5 × 10 16 ≈ 4.99 × 10 22
Number of holes = n h
In thermal equilibrium, the concentrations of electrons and holes in a semiconductor are related as: n e n h = n i2
Therefore, nh = n i2 / ne = (1.5x1016)2 / 4.99 x 1022 ≈ 4.51 x 109
Therefore, the number of electrons is approximately 4.99 × 10 22 and the number of holes is about 4.51 × 10 9 . Since the number of electrons is more than the number of holes, the material is an n-type semiconductor.
More Questions From Class 12 Physics - Chapter Semiconductor Electronics
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A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm?
- Q:-
In an unbiased p-n junction, holes diffuse from the p-region to n-region because
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(c) hole concentration in p-region is more as compared to n-region.
(d) All the above.
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(b) Electrons are minority carriers and pentavalent atoms are the dopants.
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For a transistor amplifier, the voltage gain
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Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to (E g ) C , (E g ) Si and (E g ) Ge . Which of the following statements is true?
(a) (E g ) Si < (E g ) Ge < (E g ) C
(b) (E g ) C < (E g ) Ge > (E g ) Si
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(d) (E g ) C = (E g ) Si = (E g ) Ge
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