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Physics · 2025 · 2 marks
Semiconductor Electronics: Materials, Devices and Simple CircuitsExtrinsic Semiconductor2 marksApplyvery short answer
CBSE 2025 · Region 4 · Set 2 · Q17
In an intrinsic semiconductor, carrier's concentration is 5 × 10^8 m^-3. On doping with impurity atoms, the hole concentration becomes 8 × 10^12…
In an intrinsic semiconductor, carrier's concentration is $\displaystyle 5 \times 10^{8} \mathrm{~m}^{-3}$. On doping with impurity atoms, the hole concentration becomes $\displaystyle 8 \times 10^{12} \mathrm{~m}^{-3}$.
(a)
Identify (i) the type of dopant and (ii) the extrinsic semiconductor so formed.
(b)
Calculate the electron concentration in the extrinsic semiconductor.
Marking-scheme solution
(a)(i)
Trivalent
(ii)
p-type semiconductor
(b)
Electron concentration:
$\displaystyle n_{e}=\frac{n_{i}^{2}}{n_{h}}$
$\displaystyle n_{e}=\frac{\left(5 \times 10^{8}\right)^{2}}{8 \times 10^{12}}$
$\displaystyle n_{e}=3.125 \times 10^{4} \mathrm{~m}^{-3}$
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