Tag: semiconductor electronics: materials, devices and simple circuits

Questions Related to semiconductor electronics: materials, devices and simple circuits

Choose the wrong statement

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

  1. p-type semi conductor is positively charged

  2. n-type semi conductor is negatively charged

  3. both p-type and n-type are electrically neutral

  4. none of these

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Correct Option: C
Explanation:

p and n type materials are NOT positively and negatively charged. An n-type material by itself has mainly negative charge carriers (electrons) which are able to move freely, but it is still neutral because the fixed donor atoms, having donated electrons, are positive

In N -- type semi  - conductor current is due to

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

  1. Electrons

  2. Holes

  3. Electrons and holes

  4. none of these

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Correct Option: A
Explanation:

In N-type semi-conductor majority carriers are electrons. So, when the voltage is applied across the semi-conductor electrons started to drift from negative to positive terminal as result current starts to flow in opposite direction of electrons.

Hence in N- type semi-conductor current is due to electrons.

Fermi level of energy of an intrinsic semiconductor lies

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

  1. in the middle of the forbidden gap.

  2. below the middle of forbidden gap.

  3. above the middle of forbidden gap.

  4. outside the forbidden gap.

Show answer
Correct Option: A
Explanation:

Fermi energy is determined as the energy point where the probability of occupancy by an electron is exactly $50\ %$ or $0.5$, i.e., $\dfrac{1}{2}$. For the intrinsic semiconductor, since electrons and holes are always created in pairs, $n = p = ni$. Hence, there are equal number of holes and electrons in valence band and conduction band respectively. Therefore, the Fermi energy level lies in the middle of the forbidden gap, i.e., energy band gap.

In a p-type semiconductor, the acceptor valence band is

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

  1. close to the valence band of the host crystal

  2. close to conduction band of the host crystal

  3. below the conduction band of the host crystal

  4. above the conduction band of the host crystal

Show answer
Correct Option: A
Explanation:

The acceptor valence band is close to the valence band of host crystal

In an n-type semiconductor, donor valence band is

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

  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

Show answer
Correct Option: C
Explanation:

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

An intrinsic semiconductor at the absolute zero temperature ________.

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

  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

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Correct Option: B
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.

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

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

  1. intrinsic

  2. extrinsic

  3. doped semiconductor

  4. active semiconductor

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Correct Option: B
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.

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

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

  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 $Si$

Show answer
Correct Option: B
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

Give two example of intrinsic semiconductor?

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

  1. aluminum

  2. Silicon, germanium

  3. copper

  4. nitrogen

Show answer
Correct Option: B
Explanation:
all other options except silicon,germanium are not semiconductors.
so the answer is silicon and germanium

Doping of intrinsic semiconductor is done

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

  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

Show answer
Correct Option: B
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.