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⚛️ Physics  ·  Semiconductor Electronics  ·  NEET & JEE

In an n-type silicon sample the intrinsic concentration is 1.5 × 1016 m-3 and the electron concentration is 5 × 1022 m-3. The hole concentration is:

Answer: 4.5×109 m-3.

  • A 2.25×109 m-3
  • B 5×1022 m-3
  • C 4.5×109 m-3
  • D 1.5×1016 m-3

Correct answer: C. 4.5×109 m-3

Explanation: By the mass-action law nenh = ni2, so nh = (1.5 × 1016)2/(5 × 1022) = 4.5 × 109 m-3.

Conductorconduction bandvalence bandbands overlapSemiconductorconduction bandvalence bandsmall gap (~1 eV)Insulatorconduction bandvalence bandlarge gap(> 3 eV)

Conductors have overlapping bands, semiconductors have a small energy gap that can be bridged by heat or doping, and insulators have a large gap that blocks conduction.

Concept context

Band theory, p-n junction, diodes, transistors, logic gates, and integrated circuits.

Read the full Semiconductor Electronics notes →