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MHT CET · Physics · Semiconductors

Pure Silicon crystal at \(300 \mathrm{~K}\) has equal electron and hole concentration of \(1.5 \times 10^{16} \mathrm{~m}^{-3}\). Doping by indium increases \(n_h=4.5 \times 10^{22} \mathrm{~m}^{-3}\). The \(n_e\) in the doped silicon is:

  1. A \(5 \times 10^9\)
  2. B \(2.25 \times 10^{10}\)
  3. C \(3 \times 10^{12}\)
  4. D \(9 \times 10^6\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(5 \times 10^9\)

Step-by-step Solution

Detailed explanation

In an extrinsic semiconductor:
\(\begin{aligned} & n_e n_h=\left(n_i\right)^2 \\ & n_e \times 4.5 \times 10^{22}=\left(1.5 \times 10^{16}\right)^2 \\ & n_e=\frac{2.25 \times 10^{32}}{4.4 \times 10^{22}} \\ & \therefore n_e=5 \times 10^9\end{aligned}\)