Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 × 1016 m ⁻³. Doping by indium increases nh to 4.5 × 1022 m ⁻³. The doped semiconductor is of (a) p-type having electron concentration ne = 5 × 109 m ⁻³ (b) n-type with electron concentration ne = 5 × 1022 m ⁻³ (c) p-type with electron concentration ne = 2.5 × 1010 m ⁻³ (d) n-type with electron concentration ne = 2.5 × 1023 m ⁻³

Answer: (a). Indium is trivalent, so the doped Si is p-type. ne = (ni²)/(nh) = (1.5×10¹⁶)²4.5×10²² = 2.25×10³²4.5×10²² ne = 5×10⁹ m⁻³ So the answer is (a) p-type with ne = 5×10⁹ m⁻³.

Pure Si at 500 K has equal number of electron (ne) and hole (nh)… | NEET 2011 (AIPMT, Mains)

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Intrinsic & Extrinsic Semiconductors

Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 $\times$ 1016 m ${}^{-3}$ . Doping by indium increases nh to 4.5 $\times$ 1022 m ${}^{-3}$ . The doped semiconductor is of

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Answer: (a)

Indium is trivalent, so the doped Si is p-type.
$n_e = \dfrac{n_i^2}{n_h} = \dfrac{(1.5\times10^{16})^2}{4.5\times10^{22}} = \dfrac{2.25\times10^{32}}{4.5\times10^{22}}$
$n_e = 5\times10^{9}\ \text{m}^{-3}$
So the answer is (a) p-type with $n_e = 5\times10^9\ \text{m}^{-3}$ .

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