Energy Bands in Solids and Semiconductors

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Which of the following statements is not true ?

The resistance of intrinsic semiconductors decreases with increase of temperature.

Doping pure Si with trivalent impurities give

p

-type semiconductors.

(C)

The majority carriers in

n

-type semiconductors are holes.

(D)

p

n

junction can act as a semiconductor diode.

JEE Advanced 1997

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Holes are charge carriers in

* Multiple Correct Options

(A)

intrinsic semiconductors

(B)

ionic solids

(C)

p-type semiconductors

(D)

metals

LEVELJEE Main

The electrical conductivity of a semiconductor increases when electro magnetic radiation of wavelength shorter than $2480 nm$ is incident on it. The band gap (in $eV$ ) for the semiconductor is

(A)

0.9

(B)

0.7

(C)

0.5

(D)

1.1

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The impurity atoms with which pure silicon should be doped to make a $p$ -type semiconductor are those of

* Multiple Correct Options

When a potential difference is applied across, the current passing through

* Multiple Correct Options

(A)

an insulator at

0 K

is zero

(B)

a semiconductor at

0 K

is zero

(C)

a metal at

0 K

is finite

(D)

p

n

diode at

300 K

is finite, if it is reverse biased

LEVELJEE Main

The manifestation of band structure in solids is due to

(A)

Heisenberg's uncertainty principle

(B)

Pauli's exclusion principle

(C)

Bohr's correspondence principle

For extrinsic semiconductors when doping level is increased,

(A)

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

(B)

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

(C)

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

(D)

Fermi level of both p-type and n-type semiconductors will go upward for

T > T_{F}

K and downward for

T < T_{F}

K, where

T_{F}

is Fermi temperature

JEE Main 2021

LEVELJEE Main

In a semiconductor, the number density of intrinsic charge carriers at $2 7^{\circ} C$ is $1.5 \times 1 0^{16} / m^{3}$ . If the semiconductor is doped with impurity atom, the hole density increases to $4.5 \times 1 0^{22} / m^{3}$ . The electron density in the doped semiconductor is ...... $\times 1 0^{9} / m^{3}$ .

LEVELJEE Main

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

(A)

All

E_{c}, E_{g}, E_{v}

increase

(B)

E_{c}

and

E_{v}

increase but

E_{g}

decreases

(C)

E_{c}

and

E_{v}

decrease but

E_{g}

increases

(D)

All

E_{c}, E_{g}, E_{v}

decrease

LEVELJEE Main

Carbon, silicon and germanium have four valence electrons each. At room temperature, which one of the following statements is most appropriate? [AIEEE 2007]

(A)

The number of free conduction electrons is significant in C but small in Si and Ge

(B)

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

(C)

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

(D)

The number of free electrons for conduction is significant only in Si and Ge but small is C

LEVELJEE Main

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?

(A)

\frac{5}{8}

(B)

\frac{4}{5}

(C)

\frac{5}{4}

(D)

\frac{4}{7}

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The energy band gap is maximum in

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480 nm$ , is incident on it. The band gap in (eV) for the semiconductor is

(A)

1.1 eV

(B)

2.5 eV

(C)

0.5 eV

(D)

0.7 eV

JEE Main 2021

LEVELJEE Main

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.

JEE Main 2019

LEVELJEE Main

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 $1 0^{19} m^{- 3}$ and their mobility is $1.6 m^{2} (V-s)^{- 1}$ , 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)

0.2 Ω -m

(C)

0.4 Ω -m

(D)

4 Ω -m

LEVELJEE Main

A piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of

(A)

each of them increases

(B)

each of them decreases

(C)

copper decreases and germanium increases

(D)

copper increases and germanium decreases

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At absolute zero, Si acts as

Which of the following statements is not true ?

Holes are charge carriers in

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The impurity atoms with which pure silicon should be doped to make a p-type semiconductor are those of

When a potential difference is applied across, the current passing through

The manifestation of band structure in solids is due to

For extrinsic semiconductors when doping level is increased,

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

Carbon, silicon and germanium have four valence electrons each. At room temperature, which one of the following statements is most appropriate? [AIEEE 2007]

The energy band gap is maximum in

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 piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of

At absolute zero, Si acts as

The impurity atoms with which pure silicon should be doped to make a $p$ -type semiconductor are those of