Q. No.Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy gaps represented by \(\left(E_g\right)_C,(E_g)_{Si}~\text{and}~(E_g)_{Ge}\) respectively. Which one of the following relationships is true in their case?
1.
\(\left(E_g\right)_C<\left(E_g\right)_{G e} \)
2.
\(\left(E_g\right)_C>\left(E_g\right)_{S i} \)
3.
\(\left(E_g\right)_C=\left(E_g\right)_{S i} \)
4.
\(\left(E_g\right)_C<\left(E_g\right)_{S i}\)
In the given figure, the potential difference between A and B is:
| 1. | 0 | 2. | 5 volt |
| 3. | 10 volt | 4. | 15 volt |
A semiconductor is known to have an electron concentration of cm-3 and a hole concentration of cm-3. The semiconductor is:
1. n-type
2. p-type
3. intrinsic
4. insulator
When a p-n junction is forward biased, then:
| 1. | the depletion region becomes thick. |
| 2. | the p-side is at a higher potential than n side. |
| 3. | the current flowing is zero. |
| 4. | the effective resistance is of the order of \(10^6 ~\Omega\). |
If a small amount of aluminium is added to the silicon crystal:
| 1. | its resistance decreases. |
| 2. | it becomes a p-type semiconductor. |
| 3. | there will be fewer free electrons than holes in the semiconductor. |
| 4. | All of these are correct. |
If in a p-n junction, a square input signal of 10 V is applied as shown, then the output across RL will be:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
Pure Si at 500 K has equal number of electron and hole concentration of Doping by indium increases to The doped semiconductor is of:
| 1. | n-type with electron concentration \(n_{e}=5\times10^{22}~m^{-3}\) |
| 2. | p-type with electron concentration \(n_{e}=2.5\times10^{23}~m^{-3}\) |
| 3. | n-type with electron concentration \(n_{e}=2.5\times10^{10}~m^{-3}\) |
| 4. | p-type with electron concentration \(n_{e}=5\times10^{9}~m^{-3}\) |
In a PN-junction diode:
| 1. | the current in the reverse biased condition is generally very small. |
| 2. | the current in the reverse biased condition is small but the forward-biased current is independent of the bias voltage. |
| 3. | the reverse-biased current is strongly dependent on the applied bias voltage. |
| 4. | the forward-biased current is very small in comparison to reverse-biased current. |
Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be:
| 1. | In the circuit (1) and (2) |
| 2. | In the circuit (2) and (3) |
| 3. | In the circuit (1) and (3) |
| 4. | Only in the circuit (1) |
How much is the forbidden gap (approximately) in the energy bands of germanium at room temperature?
1. \(1.1~\text{eV}\)
2. \(0.1~\text{eV}\)
3. \(0.67~\text{eV}\)
4. \(6.7~\text{eV}\)
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