Tag: semiconductors

Questions Related to semiconductors

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480nm$ is incident on it The forbidden band gap for the semiconductor is 

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $0.9eV$

  2. $0.7eV$

  3. $0.5eV$

  4. $1.1eV$

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Correct Option: C

In germanium crystal, the forbidden energy gap in joule is:

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $1.6\times 10^{-19}$

  2. zero

  3. $1.12\times 10^{-19}$

  4. $1.76\times 10^{-19}$

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Correct Option: C

The energy of radiation emitted by $LED$ is :

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. greater than the band gap of the semiconductor used

  2. always less than the band gap of the semiconductor used.

  3. always equal to the band gap of the semiconductor used.

  4. equal to the or less than the band gap of the semiconductor used

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Correct Option: D

Given that the mobility of electrons in Ge is $0.4$ metre square/volt sec and electronic charge is $ 1.6 \times 10^{-19}$C. How many door atom (per $ m^3$) have in semiconductor of conductivity $500$ mho/m:-

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $ 8 \times 10^{21}$

  2. $8 \times 10^{15}$

  3. $5 \times 10^{21}$

  4. $8 \times 10^6$

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Correct Option: C

Three semiconductors are arranged in the increasing order of their energy gap as follows: the correct arrangement is

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Tellurium, germanium, silicon

  2. Tellurium,silicon , germanium

  3. silicon, germanium, Tellurium

  4. silicon, Tellurium, germanium

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Correct Option: A

Depletion layer consists of:

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. electrons

  2. protons

  3. mobile ions

  4. immobile ions

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Correct Option: D

The band gap for a pure semi-colour is $2.1\ eV$. The maximum wavelength of a photon which is able to create a hole-electron pair is:

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $600\ nm$

  2. $589\ nm$

  3. $400\ nm$

  4. $none\ of\ these$

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Correct Option: B

State whether true or false:

The highest occupied energy band is called the valence band and the lowest unoccupied energy band is called the conduction band.

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. True

  2. False

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Correct Option: A
Explanation:

The highest occupied energy band is called the valence band and the lowest unoccupied energy band is called the conduction band.
Their difference determines the conductivity of the compound.

The highest occupied energy band is called ________ and lowest unoccupied energy band is called the _________ .

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Band Gap, Conduction band

  2. Valence band, Band Gap

  3. Conduction band, Valence band

  4. Valence band, Conduction band

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Correct Option: C
Explanation:

The highest energy band occupied by electrons is the valence band. In a conductor, the valence band is partially filled, and since there are numerous empty levels, the electrons are free to move under the influence of an electric field; thus, in a metal the valence band is also the conduction band. The valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states. This distinction is meaningless in metals as the highest band is partially filled, taking on the properties of both the valence and conduction bands.


In metals, the conduction bands are incompletely filled orbitals that allow electrons to flow.

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. true

  2. false

  3. orbit

  4. none of these

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Correct Option: A
Explanation:

In metals, the conduction bands are incompletely filled orbitals that allow electrons to flow. This helps in electrical conductivity. If the conduction band is completely filled, then there is no flow of electrons and the conductor becomes insulator.