Q. No.Identify the incorrect statement from the following:
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). |
(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. | \(4.5\times10^{9}~\text{m}^{-3}, 4.5\times 10^{9}~\text{m}^{-3}\) |
Why can't we take one slab of p-type semiconductor and physically join it to another slab of n-type semiconductor to get a p-n junction?
| 1. | the diffusion of majority charge carriers will not occur. |
| 2. | the junction will behave as a discontinuity for the flowing charge carriers. |
| 3. | the junction will behave as a continuity for the flowing charge carriers. |
| 4. | both (1) and (2). |
The \((V\text-I)\) characteristic of a silicon diode is shown in the figure. The resistance of the diode at \(V_D=-10\) V is:
1. \(1\times10^7~\Omega~\)
2. \(2\times10^7~\Omega~\)
3. \(3\times10^7~\Omega~\)
4. \(4\times10^7~\Omega~\)
| 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 \(n_e=2.5\times10^{23}~\text{m}^{-3}\). |
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 |
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
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