Mobility

 

The conductivity arises form mobile charge carriers of the semiconductor. 

Types of matter	Mobile charge carriers
Metal	Electrons
Ionized gas	Electrons & positive charged ions
Electrolyte	Position ions and negative ions

 

Bohr's Atomic Model

 

The atomic model is proposed by Bohr in 1913. The Bohr has made following assumptions.

• The atom has massive positive charged nucleus.
• The electrons revolve round their nucleus in circular orbits. The centrifugal force between electron and nucleus is balanced by electrostatic pull.

Harmonic Resonance

 

• Sometimes harmonic resonance occurs between power capacitor and transformer which may cause high magnification of harmonics. 
• The resonance can happen at one particular frequency is called as resonance frequency ( f_r )  in a system in which inductive reactance       ( X_L ) and capacitive reactance ( X_C ). 
• The net impedance becomes low when the inductive reactance X_L is equal to capacitive reactance X_C. 

Atoms, Molecules & Ions

 

Atoms

• The smallest particle of any object is called as atoms. 
• Every object is made of atoms. 
• However, the entire world is made of matters. 
• The atoms are very small and they measured in the nanometers.

Atom

• According to Bohr , an atom is composed by number of electrons moves in circular or elliptical orbits around the center nucleus. 
• The nucleus consists of protons and neutrons.
• Mass of electron = 9.1 × 10 ^{– 31} kg
• Charge of electron = 1.6 × 10 ^{– 19} coulomb

Diffusion

It is defined as the flow of charge from high density region to low density region without any external applied field. 

• The flow of charge is due to non - uniform distribution of charge carriers in the semiconductor crystal. 
• This will result in flow of current without any external applied field. 

Drift & Drift Velocity

• The directed motion of the charge carriers ( electrons + holes ) in the semiconductor done mainly by ( 1 ) Charge drift ( flow ) under the influence of electric field ( 2 ) Charge drift from high charge density to low charge density