Conductors, Insulators and Semiconductors
What are insulators?
Insulators
• Materials that do not conduct electrical current
• Mostly compounds rather than single element materials
• Very high resistivity
• Valence electrons are tightly bound to the atom
• Examples: rubber, plastic, glass, quartz, What are conductors?
What are conductors?
• Materials that easily conduct electrical current
• Mostly single element materials like metals
• Characterized by one valence electron loosely b
bound to the atom
d
h
• Examples: copper, silver, gold aluminum
What are semiconductors?
Semiconductors
• Materials that are between conductors and insulators in its ability to conduct electrical current
• Neither a good conductor nor a good insulator Neither a good conductor nor a good insulator
in its intrinsic (pure) state
• Characterized by four valence electrons
• Examples: antimony, arsenic, astatine, boron, polonium, tellurium, silicon, germanium
What is a band gap?
Band Gap
• difference in energy between the valence band and the conduction band of an atom
What is a crystal?
What is a Electron Current?
Electron Current
• movement of free electrons in a semiconductive material
What is a Hole Current?
Doping
• Increasing conductivity by controlled addition of impurities to the intrinsic material
What is doping?
N Type Semiconductors
What are N Type Semiconductors?
• Produced by adding pentavalent impurity atoms to increase the number of conduction‐
band electrons in intrinsic silicon
P Type Semiconductors
What are P Type Semiconductors?
What is a PN Junction?
• Produced by adding trivalent impurity atoms to increase the number of holes in intrinsic silicon