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MHT CET 2021 (21 Sep, Shift 1) · Intrinsic & Extrinsic Semiconductors

Intrinsic & Extrinsic Semiconductors question from MHT CET 2021 (21 Sep, Shift 1)

Q35MHT CET 2021 · 21 SEP · SHIFT 1Easy

Intrinsic & Extrinsic Semiconductors

In a pure silicon, number of electrons and holes per unit volume are 1.6×1016 m−31.6 \times 10^{16}\text{ m}^{-3}. If silicon is doped with Boron in a way that on doping hole density increases to 4×1022 m−34 \times 10^{22}\text{ m}^{-3}. Then electron density in doped semiconductor will be

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Answer: (b)

  1. Mass action law: ne=ni2nhn_e = \dfrac{n_i^2}{n_h}
  2. ne=(1.6×1016)24×1022=2.56×10324×1022n_e = \dfrac{(1.6\times10^{16})^2}{4\times10^{22}} = \dfrac{2.56\times10^{32}}{4\times10^{22}}
  3. ne=6.4×109 m−3n_e = 6.4\times10^{9}\ \text{m}^{-3}
  4. So the answer is (b).
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