- 1(current)
Q. No.Hole is:
| 1. | an anti-particle of electron. |
| 2. | a vacancy created when an electron leaves a covalent bond. |
| 3. | absence of free electrons. |
| 4. | an artificially created particle. |
Let \(n_{p}\) and \(n_{e}\) be the number of holes and conduction electrons in an intrinsic semiconductor. Then:
1. \(n_{p}> n_{e}\)
2. \(n_{p}= n_{e}\)
3. \(n_{p}< n_{e}\)
4. \(n_{p}\neq n_{e}\)
A \(\mathrm{p}\text-\)type semiconductor is:
| 1. | positively charged |
| 2. | negatively charged |
| 3. | uncharged |
| 4. | uncharged at \(0~\text{K}\) but charged at higher temperatures |
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. |
In semiconductors, which of the following gives the law of mass action?
(where symbols have their usual meanings.)
1. \(n_i=n_e=n_h\)
2. \(n_i^2=n_en_h\)
3. \(n_h>> n_e\)
4. \(n_h<<n_e\)
| 1. | flow in the direction of the \(\overrightarrow E\) and cause a current opposite to \(\overrightarrow E\) |
| 2. | flow opposite to \(\overrightarrow E\) and cause a current along \(\overrightarrow E\) |
| 3. | flow along \(\overrightarrow E\) and cause a current along \(\overrightarrow E\) |
| 4. | flow opposite to \(\overrightarrow E\) and cause a current opposite to \(\overrightarrow E\) |
Pure Si at \(500~\text{K}\) has an equal number of electron \((n_e)\) and hole\((n_h)\) concentrations of \(1.5\times10^{16}~\text{m}^{-3}\). Doping by indium increases \(n_h\) to \(4.5\times10^{22}~\text{m}^{-3}\). The doped semiconductor is of:
| 1. | \(p\)-type with electron concentration \(n_e=5\times10^9~\text{m}^{-3}\) |
| 2. | \(n\)-type with electron concentration \(n_e=5\times10^{22}~\text{m}^{-3}\) |
| 3. | \(p\)-type with electron concentration \(n_e=2.5\times10^{10}~\text{m}^{-3}\) |
| 4. | \(n\)-type with electron concentration \(n_e=2.5\times10^{23}~\text{m}^{-3}\) |
When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor,
1. increases
2. decreases
3. remains the same
4. becomes zero
Suppose a pure Si crystal has \(5\times10^{28}~\text{atoms m}^{-3}\). It is doped by a \(1\) ppm concentration of pentavalent As. The number of electrons and holes are, respectively: (Given: \(n_i=1.5\times10^{16}~\text{m}^{-3}\))
| 1. | \(5\times10^{22}~\text{m}^{-3}, 4.5\times10^{9}~\text{m}^{-3}\) |
| 2. | \(4.5\times10^{9}~\text{m}^{-3}, 5\times 10^{22}~\text{m}^{-3}\) |
| 3. | \(5\times10^{22}~\text{m}^{-3}, 5\times10^{22}~\text{m}^{-3}\) |
| 4. | \(4.5\times10^{9}~\text{m}^{-3}, 4.5\times 10^{9}~\text{m}^{-3}\) |
| 1. | antimony | 2. | phosphorous |
| 3. | arsenic | 4. | boron |
- 1(current)
Q. No.
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