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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Semiconductors and Semiconductor Devices

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Semiconductors and Semiconductor Devices

Suppose n_p and n_e denote the numbers of holes and conduction...

Suppose npn_p and nen_e denote the numbers of holes and conduction electrons in an extrinsic semiconductor.

Options

  1. Anp<nen_p < n_e
  2. Bnp≠nen_p \neq n_e
  3. Cnp=nen_p = n_e
  4. Dnp>nen_p > n_e

Correct answer

B. np≠nen_p \neq n_e

Step-by-step solution

In an intrinsic semiconductor, the number of holes is equal to the number of conduction electrons, giving np=nen_p = n_e.

An extrinsic semiconductor is formed by doping an intrinsic semiconductor with either pentavalent or trivalent impurities.

For an n-type semiconductor, electrons are the majority charge carriers, so ne>npn_e > n_p.

For a p-type semiconductor, holes are the majority charge carriers, so np>nen_p > n_e.

Therefore, in any extrinsic semiconductor, the number of holes is never equal to the number of conduction electrons, which implies np≠nen_p \neq n_e.
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