Topic 1 : Semiconductor Material - 1

1. ⇒  (JEE Main 2023 (Online) 6th April Morning Shift)

The resistivity ( ρ ) of semiconductor varies with temperature. Which of the following curve represents the correct behaviour

A.

JEE Main 2023 (Online) 6th April Morning Shift Physics - Semiconductor Question 2 English Option 1

B.

JEE Main 2023 (Online) 6th April Morning Shift Physics - Semiconductor Question 2 English Option 2

C.

JEE Main 2023 (Online) 6th April Morning Shift Physics - Semiconductor Question 2 English Option 3

D.

JEE Main 2023 (Online) 6th April Morning Shift Physics - Semiconductor Question 2 English Option 4

The Correct Answer is Option (D)

Currently no explanation available

2. ⇒  (JEE Main 2023 (Online) 1st February Evening Shift)

Choose the correct statement about Zener diode :

A. It works as a voltage regulator in reverse bias and behaves like simple pn junction diode in forward bias.

B. It works as a voltage regulator in both forward and reverse bias.

C. It works as a voltage regulator only in forward bias.

D. It works as a voltage regulator in forward bias and behaves like simple pn junction diode in reverse bias.

The Correct Answer is Option (A)

Option A is the correct statement about Zener diode. It works as a voltage regulator in reverse bias and behaves like a simple pn junction diode in forward bias. When a Zener diode is reverse-biased, it operates in the breakdown region, where a relatively constant voltage is maintained across the diode, regardless of the current flowing through it. This property makes it useful as a voltage regulator. In forward bias, the voltage applied across the diode is in the same direction as the normal direction of current flow. In this condition, the Zener diode behaves like a simple pn junction diode and allows current to flow in the forward direction.

3. ⇒  (JEE Main 2023 (Online) 31st January Morning Shift)

The effect of increase in temperature on the number of electrons in conduction band ( n e ) and resistance of a semiconductor will be as:

A. n e decreases, resistance increases

B. Both n e and resistance increase

C. n e increases, resistance decreases

D. Both n e and resistance decrease

The Correct Answer is Option (C)

As temperature increases n e increases, this results in increase in conductance.

T increases, n e increases and R decreases.

4. ⇒  (JEE Main 2023 (Online) 25th January Evening Shift)

Statement I : When a Si sample is doped with Boron, it becomes P type and when doped by Arsenic it becomes N-type semi conductor such that P-type has excess holes and N-type has excess electrons.

Statement II : When such P-type and N-type semi-conductors, are fused to make a junction, a current will automatically flow which can be detected with an externally connected ameter.

In the light of above statements, choose the most appropriate answer from the options given below

A. Statement I is incorrect but statement II is correct

B. Both Statement I and statement II are correct

C. Statement I is correct but statement II is incorrect

D. Both Statement I and Statement II are incorrect

The Correct Answer is Option (C)

Statement I is correct but in statement II we cannot detect the current through ammeter thus the statement II is incorrect.

5. ⇒  (JEE Main 2021 (Online) 26th August Morning Shift)

Statement I : By doping silicon semiconductor with pentavalent material, the electrons density increases.

Statement II : The n-type semiconductor has net negative charge.

In the light of the above statements, choose the most appropriate answer from the options given below :

A. Statement - I is true but Statement - II is false.

B. Statement - I is false but Statement - II is true.

C. Both Statement I and Statement II are true.

D. Both Statement I and Statement II are false.

The Correct Answer is Option (A)

Pentavalent activities have excess free e , so e density increases but overall semiconductor is neutral.

6. ⇒  (JEE Main 2021 (Online) 25th February Evening Shift)

For extrinsic semiconductors; when doping level is increased;

A. Fermi-level of both p-type and n-type semiconductors will go upward for T > TFK and downward for T < TFK, where TF is Fermi temperature.

B. Fermi-level of p-type semiconductor will go upward and Fermi-level of n-type semiconductors will go downward

C. Fermi-level of p and n-type semiconductors will not be affected.

D. Fermi-level of p-type semiconductors will go downward and Fermi-level of n-type semiconductor will go upward.

The Correct Answer is Option (D)

In n-type semiconductor pentavalent impurity is added. Each pentavalent impurity donates a free electron. So the Fermi-level of n-type semiconductor will go upward.

And In p-type semiconductor trivalent impurity is added. Each trivalent impurity creates a hole in the valence band. So the Fermi-level of p-type semiconductor will go downward.

7. ⇒  (JEE Main 2019 (Online) 9th January Morning Slot)

Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an n-type semiconductor, the density of electrons is 1019 m 3 and their mobility is 1.6 m2/(V.s) then the resistivity of the semiconductor (since it is an n-type semiconductor contribution of holes is ignored) is close to :

A. 2 Ω m

B. 4 Ω m

C. 0.4 Ω m

D. 0.2 Ω m

The Correct Answer is Option (C)

For semiconductor,

Conductivity, σ = ne q μ e + nh q μ h

given that semiconductor is n-type. So contribution of holes is ignored.

   nh q μ h = 0

    σ = ne q μ e

Resistivity, ρ = 1 σ

= 1 n e q μ e

= 1 10 19 × 1.6 × 10 19 × 1.6

= 1 1.6 × 1.6

= 0.4 Ω m

8. ⇒  (JEE Main 2017 (Online) 8th April Morning Slot)

What is the conductivity of a semiconductor sale having electron concentration of 5 × 10 18 m 3 , hole concentration of 5 × 10 19 m 3 , electron mobility of 2.0 m2 V 1 s-1 and hole mobility of 0.01 m2 V 1 s 1 ?

(Take charge of electronas 1.6 × 10 19 c)

A. 1.68 ( Ω -m) 1

B. 1.83 ( Ω -m) 1

C. 0.59 ( Ω -m) 1

D. 1.20 ( Ω -m) 1

The Correct Answer is Option (A)

Conductivity of semiconductor,

σ = e ( η e μ e + η μ h )

= 1.6 × 10 19 (5 × 1018 × 2 + 5 × 1019 × 0.01)

= 1.6 × 1.05

= 1.68

9. ⇒  (JEE Main 2016 (Offline))

The temperature dependence of resistance of C u and undoped S i in the temperature range 300 400 K , is best described by :

A. Linear increases for C u , exponential decrease of S i .

B. Linear decrease for C u , linear decrease for S i

C. Linear increase for C u , linear increase for S i .

D. Linear increase for C u , exponential increase for S i

The Correct Answer is Option (A)

JEE Main 2016 (Offline) Physics - Semiconductor Question 186 English Explanation

10. ⇒  (AIEEE 2007)

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate ?

A. The number of free electrons for conduction is significant only in S i and G e but small in C .

B. The number of free conduction electrons is significant in C but small in S i and G e .

C. The number of free conduction electrons is negligibly small in all the three.

D. The number of free electrons for conduction is significant in all the three

The Correct Answer is Option (A)

S i and G e are semiconductors but C is an insulator. Also, the conductivity of S i and G e is more than C because the valence electrons of S i , G e and C lie in third, fourth and second orbit respectively.

11. ⇒  (AIEEE 2006)

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

A. 5 8

B. 4 5

C. 5 4

D. 4 7

The Correct Answer is Option (C)

I e I h = n e e A v e n h e A v h

7 4 = 7 5 × v e v h

v e v h = 5 4