1. | decreases for conductors but increases for semiconductors. |
2. | increases for both conductors and semiconductors. |
3. | decreases for both conductors and semiconductors. |
4. | increases for conductors but decreases for semiconductors. |
In a semiconductor,
(a) | there are no free electrons at \(0~\text{K}.\) |
(b) | there are no free electrons at any temperature. |
(c) | the number of free electrons increases with temperature. |
(d) | the number of free electrons is less than that in a conductor. |
1. | \(414\) nm | 2. | \(300\) nm |
3. | \(830\) nm | 4. | \(207\) nm |
1. | The resistivity of a semiconductor increases with an increase in temperature. |
2. | Substances with an energy gap of the order of \(10\) eV are insulators. |
3. | In conductors, the valence and conduction bands may overlap. |
4. | The conductivity of a semiconductor increases with an increase in temperature. |
Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by , and respectively. Which one of the following relationships is true in their case?
1.
2.
3.
4.
\(\mathrm{C}\), \(\mathrm{Si}\), and \(\mathrm{Ge}\) have the same lattice structure. Why is the \(\mathrm{C}\) insulator?
1. | because ionization energy for \(\mathrm{C}\) is the least in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\). |
2. | because ionization energy for \(\mathrm{C}\) is highest in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\). |
3. | the number of free electrons for conduction in \(\mathrm{Ge}\) and \(\mathrm{Si}\) is significant but negligibly small for \(\mathrm{C}\). |
4. | both (2) and (3). |
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. |