Physics

Semiconductors and Diodes

461 Questions

Semiconductors and diodes form the foundation of modern electronics, covering topics like intrinsic carrier concentration and Zener breakdown. Questions often explore the characteristics of bipolar junction transistors (BJT) and the properties of doped silicon materials. This topic is crucial for physics and electronics engineering competitive exams.

Zener diode breakdownBJT circuit analysisIntrinsic carrier concentrationDoping in semiconductorsEmitter follower circuit

Semiconductors and Diodes Questions

Multiple choice physics semiconductors integrated circuits & microprocessor integrated chips semiconductor devices

Integrated circuit is defined as:

  1. a single electronic circuit on a small plate of semiconductor material.

  2. a set of electronic circuits on one small plate of semiconductor material.

  3. a circuit capable of generating dc currents.

  4. a plate of semiconductor material used to connect external multiple circuits
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An 'integrated circuit' is an electronic circuit formed on a small piece of semiconducting material, which performs the same function as a larger circuit made from discrete components. It is also called a chip or microchip.

Multiple choice physics semiconductors integrated circuits & microprocessor integrated chips semiconductor devices

Choose the correct statement:

  1. Integrated circuits are less efficient in performance at all voltages.

  2. Integrated circuits are more efficient in performance at low voltages.

  3. Integrated circuits are less efficient in performance at high voltages.

  4. Performance of an integrated circuit is independent of the magnitude of applied voltage.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Integrated circuits are used for low voltage applications. They are low power devices for use in application like microprocessor chips. 
For high voltage devices like transformers, conventional circuits are used.

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

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

  1. Electrons

  2. Holes

  3. Electrons and holes

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

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

Fermi level of energy of an intrinsic semiconductor lies

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

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

Semiconductors those are created by doping an intrinsic semiconductor with donor impurities are

  1. p-type

  2. n-type

  3. may be any of them

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

Donor impurities are the ones that donate electrons to the semiconductor atom. For each donor atom added, there is one electron donated to the semiconductor atom. As a result, the electrons in such type of semiconductors are majority charge carriers. Therefore, this extrinsic semiconductor formed by adding donor impurities are called n-type semiconductors.

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

Transistors (devices that enable current switching) make use of

  1. Intrinsic semiconductor

  2. Extrinsic semiconductor

  3. both of them

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

A transistor is a device which consists of a thin layer of one type of extrinsic semiconductor sandwiched between two thick layers of other types of extrinsic semiconductor. There are two types of transistors:

  1. pnp transistor and,
  2. npn transistor
    So, a transistor is made of extrinsic semiconductor.

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

 A semiconductor diode (devices that allow current in only one direction) consists of 

  1. Intrinsic semiconductor

  2. Extrinsic semiconductor

  3. both of them

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

A semiconductor diode consists of p-n junction having metallic contacts at both the ends. A single piece of a semiconductor material (either Si or Ge) with one portion doped with a pentavalent impurity and other portion doped with trivalent impurity behaves as a p-n junction. Means, extrinsic semiconductor or semiconductor doped with impurities of both p and n are used in p-n junction diode.

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

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

  1. phosphorus

  2. antimony

  3. boron

  4. aluminium
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

p type semiconductor has more number of holes than electrons.
P-type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities like boron, aluminium and other group IIIA elements