Majority Charge Carrier & Minority Charge Carrier

• There are no free charge carriers at 0 ^oK in the pure Silicon / Germanium.
•  However, when the room temperature increases, some of the covalent bonds are broken by heat energy. 
• This will result in electron – hole pairs are produced; it is called as thermally generated charge carriers. 

Mobile Charge Carriers & Immobile Ions

 

P type semiconductor

• The P type semiconductor material is formed by addition of acceptor type impurity atoms ( gallium, indium, aluminum, boron ) to pure silicon / germanium crystals. 
• The number of holes added is equal to the number of boron atoms ( acceptor impurities ) because each atoms contribute one hole. 

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