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PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365549 If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$ , then what is the ratio of their drift velocities?

1

\frac{2}{3}

2

\frac{4}{7}

3

\frac{5}{4}

4

\frac{1}{5}

Explanation:

$I = n e A v_{d} \Rightarrow v_{d} \propto \frac{I}{n}$
$\frac{v_{d_{1}}}{v_{d_{2}}} = \frac{I_{1}}{I_{2}} \times \frac{n_{2}}{n_{1}} = \frac{7}{4} \times \frac{5}{7} = \frac{5}{4}$

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365550 Assertion :
When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases.
Reason :
A donor impurity is an atom with valence electrons of five always.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Doping with a donor impurity (like $P, As$ ) in a semiconductor creates n-type semiconductors, where the extra free electron increases electron concentration. So correct option is (2).

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365551 When a small amount of impurity atoms are added to a semi conductor, then generally its resistivity

1 May increase or decrease depending upon the percentage of doping

2 Increase

3 Decrease

4 Does not change

Explanation:

The conductivity of a semi conductor is given by $σ = n_{e} e μ_{e} + n_{h} e μ_{h}$
where $n_{e} & n_{h} =$ number of electrons and holes per unit volume
and $μ_{e} & μ_{h} =$ mobility of electrons and holes
When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity increases and hence the resitivity.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365552 Which one of the following statement is false?

1 Pure Si doped with trivalent impurities gives a

p

- type semiconductor

2 Majority carriers in a

n

-type semiconductor are holes

3 Minority carriers in a

p

-type semiconductor are electrons

4 The resistance of intrinsic semiconductor decreases with increase of temperature

Explanation:

$p$ - type semiconductors are obtained by adding a small amount of trivalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - holes
Minority charge carriers - electrons
$n$ -type semiconductors are obtained by adding a small amount of pentavalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - electrons
The resistance of intrinsic semiconductors decreases with increase of temperature.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365553 A specimen of silicon is to be made $p$ -type semiconductor, for this one atom of indium, on an average, is doped in $5 \times 10^{7}$ silicon atoms. If the number density of silicon is $5 \times 10^{28} a t o m / m^{3}$ , then the number of acceptor atoms per $c m^{3}$ will be

1

2.5 \times 10^{30}

2

1.0 \times 10^{13}

3

1.0 \times 10^{15}

4

2.5 \times 10^{36}

Explanation:

Given, one Indium atom was doped in $5 \times 10^{7}$ Silicon atoms.
Number density of Silicon
$= 5 \times 10^{28} a t o m m^{- 3}$
$\approx 5 \times 10^{22} a t o m c m^{- 3}$
Number of acceptor atoms per $c m^{- 3}$ given by
$N_{A} = \frac{5 \times 10^{22}}{5 \times 10^{7}} = 1 \times 10^{15} c m^{- 3}$

AIIMS - 2017

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365549 If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$ , then what is the ratio of their drift velocities?

1

\frac{2}{3}

2

\frac{4}{7}

3

\frac{5}{4}

4

\frac{1}{5}

Explanation:

$I = n e A v_{d} \Rightarrow v_{d} \propto \frac{I}{n}$
$\frac{v_{d_{1}}}{v_{d_{2}}} = \frac{I_{1}}{I_{2}} \times \frac{n_{2}}{n_{1}} = \frac{7}{4} \times \frac{5}{7} = \frac{5}{4}$

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365550 Assertion :
When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases.
Reason :
A donor impurity is an atom with valence electrons of five always.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Doping with a donor impurity (like $P, As$ ) in a semiconductor creates n-type semiconductors, where the extra free electron increases electron concentration. So correct option is (2).

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365551 When a small amount of impurity atoms are added to a semi conductor, then generally its resistivity

1 May increase or decrease depending upon the percentage of doping

2 Increase

3 Decrease

4 Does not change

Explanation:

The conductivity of a semi conductor is given by $σ = n_{e} e μ_{e} + n_{h} e μ_{h}$
where $n_{e} & n_{h} =$ number of electrons and holes per unit volume
and $μ_{e} & μ_{h} =$ mobility of electrons and holes
When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity increases and hence the resitivity.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365552 Which one of the following statement is false?

1 Pure Si doped with trivalent impurities gives a

p

- type semiconductor

2 Majority carriers in a

n

-type semiconductor are holes

3 Minority carriers in a

p

-type semiconductor are electrons

4 The resistance of intrinsic semiconductor decreases with increase of temperature

Explanation:

$p$ - type semiconductors are obtained by adding a small amount of trivalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - holes
Minority charge carriers - electrons
$n$ -type semiconductors are obtained by adding a small amount of pentavalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - electrons
The resistance of intrinsic semiconductors decreases with increase of temperature.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365553 A specimen of silicon is to be made $p$ -type semiconductor, for this one atom of indium, on an average, is doped in $5 \times 10^{7}$ silicon atoms. If the number density of silicon is $5 \times 10^{28} a t o m / m^{3}$ , then the number of acceptor atoms per $c m^{3}$ will be

1

2.5 \times 10^{30}

2

1.0 \times 10^{13}

3

1.0 \times 10^{15}

4

2.5 \times 10^{36}

Explanation:

Given, one Indium atom was doped in $5 \times 10^{7}$ Silicon atoms.
Number density of Silicon
$= 5 \times 10^{28} a t o m m^{- 3}$
$\approx 5 \times 10^{22} a t o m c m^{- 3}$
Number of acceptor atoms per $c m^{- 3}$ given by
$N_{A} = \frac{5 \times 10^{22}}{5 \times 10^{7}} = 1 \times 10^{15} c m^{- 3}$

AIIMS - 2017

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365549 If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$ , then what is the ratio of their drift velocities?

1

\frac{2}{3}

2

\frac{4}{7}

3

\frac{5}{4}

4

\frac{1}{5}

Explanation:

$I = n e A v_{d} \Rightarrow v_{d} \propto \frac{I}{n}$
$\frac{v_{d_{1}}}{v_{d_{2}}} = \frac{I_{1}}{I_{2}} \times \frac{n_{2}}{n_{1}} = \frac{7}{4} \times \frac{5}{7} = \frac{5}{4}$

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365550 Assertion :
When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases.
Reason :
A donor impurity is an atom with valence electrons of five always.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Doping with a donor impurity (like $P, As$ ) in a semiconductor creates n-type semiconductors, where the extra free electron increases electron concentration. So correct option is (2).

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365551 When a small amount of impurity atoms are added to a semi conductor, then generally its resistivity

1 May increase or decrease depending upon the percentage of doping

2 Increase

3 Decrease

4 Does not change

Explanation:

The conductivity of a semi conductor is given by $σ = n_{e} e μ_{e} + n_{h} e μ_{h}$
where $n_{e} & n_{h} =$ number of electrons and holes per unit volume
and $μ_{e} & μ_{h} =$ mobility of electrons and holes
When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity increases and hence the resitivity.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365552 Which one of the following statement is false?

1 Pure Si doped with trivalent impurities gives a

p

- type semiconductor

2 Majority carriers in a

n

-type semiconductor are holes

3 Minority carriers in a

p

-type semiconductor are electrons

4 The resistance of intrinsic semiconductor decreases with increase of temperature

Explanation:

$p$ - type semiconductors are obtained by adding a small amount of trivalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - holes
Minority charge carriers - electrons
$n$ -type semiconductors are obtained by adding a small amount of pentavalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - electrons
The resistance of intrinsic semiconductors decreases with increase of temperature.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365553 A specimen of silicon is to be made $p$ -type semiconductor, for this one atom of indium, on an average, is doped in $5 \times 10^{7}$ silicon atoms. If the number density of silicon is $5 \times 10^{28} a t o m / m^{3}$ , then the number of acceptor atoms per $c m^{3}$ will be

1

2.5 \times 10^{30}

2

1.0 \times 10^{13}

3

1.0 \times 10^{15}

4

2.5 \times 10^{36}

Explanation:

Given, one Indium atom was doped in $5 \times 10^{7}$ Silicon atoms.
Number density of Silicon
$= 5 \times 10^{28} a t o m m^{- 3}$
$\approx 5 \times 10^{22} a t o m c m^{- 3}$
Number of acceptor atoms per $c m^{- 3}$ given by
$N_{A} = \frac{5 \times 10^{22}}{5 \times 10^{7}} = 1 \times 10^{15} c m^{- 3}$

AIIMS - 2017

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365549 If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$ , then what is the ratio of their drift velocities?

1

\frac{2}{3}

2

\frac{4}{7}

3

\frac{5}{4}

4

\frac{1}{5}

Explanation:

$I = n e A v_{d} \Rightarrow v_{d} \propto \frac{I}{n}$
$\frac{v_{d_{1}}}{v_{d_{2}}} = \frac{I_{1}}{I_{2}} \times \frac{n_{2}}{n_{1}} = \frac{7}{4} \times \frac{5}{7} = \frac{5}{4}$

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365550 Assertion :
When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases.
Reason :
A donor impurity is an atom with valence electrons of five always.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Doping with a donor impurity (like $P, As$ ) in a semiconductor creates n-type semiconductors, where the extra free electron increases electron concentration. So correct option is (2).

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365551 When a small amount of impurity atoms are added to a semi conductor, then generally its resistivity

1 May increase or decrease depending upon the percentage of doping

2 Increase

3 Decrease

4 Does not change

Explanation:

The conductivity of a semi conductor is given by $σ = n_{e} e μ_{e} + n_{h} e μ_{h}$
where $n_{e} & n_{h} =$ number of electrons and holes per unit volume
and $μ_{e} & μ_{h} =$ mobility of electrons and holes
When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity increases and hence the resitivity.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365552 Which one of the following statement is false?

1 Pure Si doped with trivalent impurities gives a

p

- type semiconductor

2 Majority carriers in a

n

-type semiconductor are holes

3 Minority carriers in a

p

-type semiconductor are electrons

4 The resistance of intrinsic semiconductor decreases with increase of temperature

Explanation:

$p$ - type semiconductors are obtained by adding a small amount of trivalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - holes
Minority charge carriers - electrons
$n$ -type semiconductors are obtained by adding a small amount of pentavalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - electrons
The resistance of intrinsic semiconductors decreases with increase of temperature.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365553 A specimen of silicon is to be made $p$ -type semiconductor, for this one atom of indium, on an average, is doped in $5 \times 10^{7}$ silicon atoms. If the number density of silicon is $5 \times 10^{28} a t o m / m^{3}$ , then the number of acceptor atoms per $c m^{3}$ will be

1

2.5 \times 10^{30}

2

1.0 \times 10^{13}

3

1.0 \times 10^{15}

4

2.5 \times 10^{36}

Explanation:

Given, one Indium atom was doped in $5 \times 10^{7}$ Silicon atoms.
Number density of Silicon
$= 5 \times 10^{28} a t o m m^{- 3}$
$\approx 5 \times 10^{22} a t o m c m^{- 3}$
Number of acceptor atoms per $c m^{- 3}$ given by
$N_{A} = \frac{5 \times 10^{22}}{5 \times 10^{7}} = 1 \times 10^{15} c m^{- 3}$

AIIMS - 2017

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365549 If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$ , then what is the ratio of their drift velocities?

1

\frac{2}{3}

2

\frac{4}{7}

3

\frac{5}{4}

4

\frac{1}{5}

Explanation:

$I = n e A v_{d} \Rightarrow v_{d} \propto \frac{I}{n}$
$\frac{v_{d_{1}}}{v_{d_{2}}} = \frac{I_{1}}{I_{2}} \times \frac{n_{2}}{n_{1}} = \frac{7}{4} \times \frac{5}{7} = \frac{5}{4}$

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365550 Assertion :
When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases.
Reason :
A donor impurity is an atom with valence electrons of five always.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Doping with a donor impurity (like $P, As$ ) in a semiconductor creates n-type semiconductors, where the extra free electron increases electron concentration. So correct option is (2).

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365551 When a small amount of impurity atoms are added to a semi conductor, then generally its resistivity

1 May increase or decrease depending upon the percentage of doping

2 Increase

3 Decrease

4 Does not change

Explanation:

The conductivity of a semi conductor is given by $σ = n_{e} e μ_{e} + n_{h} e μ_{h}$
where $n_{e} & n_{h} =$ number of electrons and holes per unit volume
and $μ_{e} & μ_{h} =$ mobility of electrons and holes
When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity increases and hence the resitivity.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365552 Which one of the following statement is false?

1 Pure Si doped with trivalent impurities gives a

p

- type semiconductor

2 Majority carriers in a

n

-type semiconductor are holes

3 Minority carriers in a

p

-type semiconductor are electrons

4 The resistance of intrinsic semiconductor decreases with increase of temperature

Explanation:

$p$ - type semiconductors are obtained by adding a small amount of trivalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - holes
Minority charge carriers - electrons
$n$ -type semiconductors are obtained by adding a small amount of pentavalent impurity to a pure sample of semiconductor ( $G e$ ).
Majority charge carriers - electrons
The resistance of intrinsic semiconductors decreases with increase of temperature.

PHXII14:SEMICONDUCTOR ELECTRONICS- MATERIALS- DEVICES AND SIMPLE CIRCUITS

365553 A specimen of silicon is to be made $p$ -type semiconductor, for this one atom of indium, on an average, is doped in $5 \times 10^{7}$ silicon atoms. If the number density of silicon is $5 \times 10^{28} a t o m / m^{3}$ , then the number of acceptor atoms per $c m^{3}$ will be

1

2.5 \times 10^{30}

2

1.0 \times 10^{13}

3

1.0 \times 10^{15}

4

2.5 \times 10^{36}

Explanation:

Given, one Indium atom was doped in $5 \times 10^{7}$ Silicon atoms.
Number density of Silicon
$= 5 \times 10^{28} a t o m m^{- 3}$
$\approx 5 \times 10^{22} a t o m c m^{- 3}$
Number of acceptor atoms per $c m^{- 3}$ given by
$N_{A} = \frac{5 \times 10^{22}}{5 \times 10^{7}} = 1 \times 10^{15} c m^{- 3}$

AIIMS - 2017