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Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

In an n-type semiconductor, donor valence band is

  1. above the conduction band of the host crystal

  2. close to the valence band of the host crystal

  3. close to the conduction band of the host crystal

  4. below the valence band of the host crystal
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The donor valence band lies little below the conduction band of the host crystal.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

An intrinsic semiconductor at the absolute zero temperature ________.

  1. behaves like a metallic conductor

  2. behaves like an insulator

  3. has a large number of holes

  4. has a large number of electrons
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An intrinsic semiconductor at 0 K, has electrons only in the valence band. Forbidden gap - 3 eV, as a result, electrons do not have sufficient energy to excite to the conduction band. Since there are no electrons in the conduction band, so it behaves as an insulator at 0 K.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

A doped intrinsic semiconductor is called a/an ________ semiconductor.

  1. intrinsic

  2. extrinsic

  3. doped semiconductor

  4. active semiconductor
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A pure semiconductor or semiconductor with no impurities is called intrinsic semiconductor. When a pure semiconductor is doped with an impurity, the process is called doping, due to increased conductivity of an extrinsic semiconductor. Such a semiconductor is called extrinsic semiconductor.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

The temperature dependence of resistances of $Cu$ and undoped $Si$ in the temperature range $300-400K$, is best described by:

  1. Linear increase for $Cu$, exponential increase for $Si$.

  2. Linear increase for $Cu$, exponential decrease for $Si$.

  3. Linear increase for $Cu$, linear decrease for $Si$

  4. Linear increase for $Cu$, linear increase for $Si$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As we know Cu is a conductor,so increase in temperature will lead to increase in resistance. 

Si is semiconductor so increase in temperature will lead to decrease in resistance. 
The electric resistance of a typical intrinsic (undoped) semiconductor decreases exponentially with temperature
$\rho ={ \rho  } _{ 0 }{ e }^{ -aT }$ where $a$ is a constant

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

Doping of intrinsic semiconductor is done

  1. To neutralize charge carriers

  2. To increase the concentration of majority charge carriers

  3. To make it neutral before disposal

  4. To carry out further purification
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Doping is the process of adding impurities to intrinsic semiconductors to alter their properties. Doping of intrinsic semiconductor is done to increase the concentration of majority charge carrier so that it can be use as p-type or n-type semiconductor in diode.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

The number density of electrons is not equal to the number density of holes

  1. Extrinsic semiconductors

  2. Intrinsic semiconductors

  3. both of them

  4. none of them
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an extrinsic semiconductor, doped with an impurity. For example, an n-type semiconductor which is formed by doping n-type impurity so that number of electrons are more than the number of holes. So, the number density of holes is not equal to the number density of electrons. Because in an extrinsic semiconductor, one of the two carriers are in abundance and the other one is in majority.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

The number density of electrons is equal to the number density of holes in

  1. Intrinsic semiconductors

  2. Extrinsic semiconductors

  3. both of them

  4. none of them
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an intinsic semiconductor number density of electrons and holes are always equal. As the number of electrons generated in the conduction band is equal to the number of holes generated in the valance band.

At absolute zero temperature valance band is completely filled and conduction band is completely empty.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

The crystals of pure elements like germanium and silicon are considered as:

  1. Intrinsic Semiconductor.

  2. Extrinsic semiconductors

  3. both of them

  4. none of them
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A pure semiconductor is called an intrinsic semiconductor. It has thermally generated current carriers. Germanium and silicon are frequently used as semiconductors. The intrinsic semiconductor has no impurity added to them.

Multiple choice intrinsic and extrinsic semiconductors types of semiconductors electronic devices semiconductor electronics: materials, devices and simple circuits physics

Which conductor has more electrical conductivity?

  1. Intrinsic semiconductors

  2. Extrinsic semiconductors

  3. Both have same.

  4. Can't compare
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The conductivity of an extrinsic semiconductor is more than that of an intrinsic semiconductor. This is because, in an intrinsic (pure) semiconductor, the carriers are only thermally generated carriers. But in extrinsic semiconductors, which is doped with a p-type or n-type impurity to form p-type and n-type semiconductor so as to increase the number of holes or number of electrons in a semiconductor respectively. More the charge carriers, more is the conductivity.