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. |
Which of the following is correct for \(\mathrm{n}\)-type semiconductors?
| 1. | electron is the majority carriers and trivalent atoms are dopants. |
| 2. | electrons are majority carriers and pentavalent atoms are dopants. |
| 3. | holes are majority carriers and pentavalent atoms are dopants. |
| 4. | holes are majority carriers and trivalent atoms are dopants. |
1. \(n_i=n_e=n_h\)
2. \(n_i^2=n_en_h\)
3. \(n_h>> n_e\)
4. \(n_h<<n_e\)
The conductivity of an n-type semiconductor whose density of conduction electrons is , Density of holes is , Mobility of conduction electrons is and Mobility of holes is will be
1.
2.
3.
4.
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 |
C and Si both have same lattice structure,having 4 bonding electrons in each.However, C is insulator whereas Si is intrinsic semiconductor. This is because
1. in case of C, the valence band is not completely filled at absolute zero temperature
2. in case of C,the condition band is partly filled even at absolute zero temperature
3. the four bonding electrons in the case of C lie in the second orbit,Whereas in the case of Si they lie in the third
4 .the four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit
If a small amount of antimony is added to germanium crystal
1. the antimony becomes an acceptor atom
2. there will be more free electrons than holes in the semiconductor
3. its resistance is increased
4. it becomes a p-type semiconductor
| 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 \(n_{e}=5\times10^{9}~\text{m}^{-3}\) |
Which one of the following statement is false?
(1) Pure Si doped with trivalent impurities gives a p-type semiconductor
(2) Majority carries in a n-type semiconductor are holes
(3) Minority carries in a p-type semiconductor are electrons
(4) The resistance of intrinsic semiconductor decreases with increase of temperature
For transistor action:
| (a) | the base, emitter and collector regions should have similar size and doping concentrations. |
| (b) | the base regions must be very thin and lightly doped. |
| (c) | the emitter-base junction is forward biased and the base-collector junction is reverse biased. |
| (d) | both the emitter-base junction as well as the base-collector junction are forward biased. |
Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)
4. (c) and (d)
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