A semiconductor is known to have an electron concentration of \(8\times 10^{13}~\text{cm}^{-3}\) and a hole concentration of \(5\times 10^{2}~\text{cm}^{-3}\). The semiconductor is:

1. \(\mathrm{n}\text-\)type 2. \(\mathrm{p}\text-\)type
3. intrinsic 4. insulator
Subtopic:  Types of Semiconductors |
 87%
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If a small amount of aluminium is added to the silicon crystal:

1. its resistance decreases.
2. it becomes a \(\mathrm{p\text-}\)type semiconductor.
3. there will be fewer free electrons than holes in the semiconductor.
4. All of these are correct.
Subtopic:  Types of Semiconductors |
 75%
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Pure \(Si\) at \(500\) K has equal number of electron \((n_i)\) and hole \((n_h)\) concentration of \(1.5\times10^{16}~\text{m}^{-3}.\) Doping by indium increases \(n_h\) to \(4.5\times 10^{22}~\text{m}^{-3}\). The doped semiconductor is of:
1. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=5\times10^{22}~\text{m}^{-3}\)
2. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=2.5\times10^{23}~\text{m}^{-3}\)
3. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=2.5\times10^{10}~\text{m}^{-3}\)
4. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=5\times10^{9}~\text{m}^{-3}\)
Subtopic:  Types of Semiconductors |
 69%
From NCERT
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A \(Ge\) specimen is doped with \(Al\). The concentration of acceptor atoms is \(\sim10^{21}~\text{atoms/m}^3\). Given that the intrinsic concentration of electron hole pairs is \(\sim10^{19}/\text{m}^3\) the concentration of electrons in the specimen is:
1. \(10^{17} / \text{m}^3 \) 2. \(10^{15} / \text{m}^3 \)
3. \(10^4 / \text{m}^3 \) 4. \(10^2 / \text{m}^3\)
Subtopic:  Types of Semiconductors |
 70%
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In a semiconducting material, the mobilities of electrons and holes are \(\mu_e\) and \(\mu_{h}\) respectively. Which of the following is true?
1. \(\mu_{e} > \mu _{h}\)
2. \(\mu_{e} < \mu _{h}\)
3. \(\mu_{e} = \mu _{h}\)
4. \(\mu_{e} <0; ~\mu _{h}>0\)

Subtopic:  Types of Semiconductors |
 68%
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The net charges on p-type semiconductor and n-type semiconductor are, respectively:

1. Positive, negative 2. Negative, positive
3. Positive, positive 4. Zero, zero
Subtopic:  Types of Semiconductors |
 67%
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