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. | 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. |
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 \(n_e=2.5\times10^{23}~\text{m}^{-3}\) |
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). |
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. | \(4.5\times10^{9}~\text{m}^{-3}, 4.5\times 10^{9}~\text{m}^{-3}\) |
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. \(4\times10^7~\Omega~\)