Semiconductor physics

What is the approximate hole density in n-type silicon with a donor concentration of 1×10¹⁶ cm⁻³ (all donors ionized, intrinsic carrier density ni = 1×10¹⁰ cm⁻³)?

  1. A1×10⁴ cm⁻³
  2. B1×10⁶ cm⁻³
  3. C1×10¹⁰ cm⁻³
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Answer: A. 1×10⁴ cm⁻³

The electron density is roughly equal to the donor concentration, n ≈ 1×10¹⁶ cm⁻³. From the law of mass action n × p = ni², p = (1×10¹⁰)² / 1×10¹⁶ = 1×10⁴ cm⁻³. Minority carriers are far fewer than majority carriers.

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