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Physics · 2025 · 2 marks
Semiconductor Electronics: Materials, Devices and Simple CircuitsExtrinsic Semiconductor2 marksApplyvery short answer
CBSE 2025 · Region 1 · Set 1 · Q21
A p-type Si semiconductor is made by doping an average of one dopant atom per 5 × 10^7 silicon atoms. If the number density of silicon atoms in the…
A p-type Si semiconductor is made by doping an average of one dopant atom per $\displaystyle 5 \times 10^{7}$ silicon atoms. If the number density of silicon atoms in the specimen is $\displaystyle 5 \times 10^{28}$ atoms $\displaystyle \mathrm{m}^{-3}$, find the number of holes created per cubic centimetre in the specimen due to doping. Also give one example of such dopants.
Marking-scheme solution
$\displaystyle 1$ dopant atom for $\displaystyle 5 \times 10^{7}$ Si atomsand number density of Si atoms $\displaystyle =5 \times 10^{28} \frac{\text { atoms }}{\mathrm{m}^{3}}$ (given)No. of holes created per $\displaystyle \mathrm{m}^{3}=\frac{5 \times 10^{28}}{5 \times 10^{7}}=10^{21}$Number of holes created per cubic centimeter $\displaystyle =\frac{10^{21}}{10^{6}}=10^{15}$Any one example of dopant - Aluminium / Indium / Gallium
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