Lecture 1 AEAV 203 (Lec Dipto Sir)

 AEAV-203

Lecture 01

• Difference between Electrical and Electronic Devices:
           
  
  
  
  
  
  
  
  Conductor

When the attraction force between proton and neutron is lower, it becomes easier to separate the electrons.

                            

Consider Cu, the electron configuration is:

Each copper atom loses one electron and becomes a positive ion. So, copper is a lattice of positive copper ions with free electrons moving between them.

Also, it is a metal. So, electrons can move freely.

Insulator

When the attraction force between proton and electron is higher, it becomes difficult to separate the electrons.

    

Keeping electricity bound within a material is the main goal of an insulator.

The tightly bound electrons are not free to be shared by neighboring atoms. The properties of rubber also cause the electrons to slow down and eventually prevent them from moving at all.

 

Semiconductor

A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electron flow.

Si is used widely as a semiconductor. 

Consider Si. Electron Configuration of Si:

In normal conditions, Si cannot conduct electricity, so we have to apply some form of external excitation/material to provide it some conductivity. 

Types of Semiconductor

Semiconductors are of 2 types:

• Intrinsic Semiconductor
• Extrinsic Semiconductor

    Intrinsic Semiconductor:

• Also called an undoped semiconductor.
• It is a pure semiconductor without any significant doping material.
• When an electric field is applied, the current can be conducted by electrons.
• Free electrons are produced due to the breaking up of covalent bonds by external energy.
• The electrons which move from the valence orbit can move through the material.
• The electric conductivity in intrinsic semiconductors is very less.

    Extrinsic Semiconductor:

• Due to the limitations of intrinsic semiconductors, extrinsic semiconductors are used.
•  To increase the conductivity of intrinsic semiconductors, impurities are added.
• Usually, one or two atoms of impurity are added per 10^6 atoms of a semiconductor.
• They are mainly of two types: N-type and P-type semiconductors.
• By substituting a Si atom with a special impurity atom (elements from Group-III or Group-V), a hole or conduction electron can be created.

      N-type Semiconductor: