CBSE Class 12 Physics Notes Chapter 14 Semiconductor Electronics - Materials, Devices and Simple Circuits

What are Semiconductors?

Semiconductors are the core fundamental materials which are used in solid-state electronic devices such as transistors, diodes etc. The material’s atomic structure decides whether the material will turn out to be a metal, semiconductor or insulator. Semiconductors could also be elements such as Ge, Si or compounds such as CdS or GaAs.

Intrinsic Semiconductors

These are the type of semiconductors devices which are pure and have charged electrons and holes which are achieved as a result of thermal excitation. The hole’s number is found equal to that of the electrons number.

Types of semiconductors

There are two types of semiconductors:

  • N-type- in here, \(n_{e}> > n_{h}\)
  • P-type- in here, \(n_{h}> >n_{e}\)

For metals, \(E_{g}\approx 0\) and for semiconductors \(E_{g}\) ranges from 0.2 eV to 3 eV and in the case of insulators \(E_{g}\)>3eV

Diode

Diodes are being for the purpose of AC voltage rectification which means restricting the voltage to follow one direction only using a capacitor or a filter, a dc voltage can be achieved. The types of diodes are:

  • Zener Diode- This is used in places where voltage regulation is needed.
  • P-N junction diode- It is used in photonic or optoelectronic devices and the entity is the photon. Examples are solar cells, light emitting diodes etc

Types of Digital Circuits

There are special logic operational digital circuits. They are:

  • NOR gate
  • NAND
  • NOT
  • AND
  • OR

 

Important Questions

  1. When a p-n junction is set to forward-biased,
    1. we could witness a rise in the potential barrier.
    2. we could see a reduction in the majority carrier current to the value zero.
    3. there is a decrease in the potential barrier.
    4. None
  2. In transistor action, identify the correct statements.
    1. The doping concentrations and size of the Base, emitter, and collector are similar
    2. The base region is found out to be thin and lightly doped
    3. The collector junction and the emitter junction is reversed biased and forward biased respectively
    4. Both the collector junction and the emitter junction are forward biased.

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