Flashcards in Semiconductor Physics Deck (27)
What was a major advantage of transistors, compared to devices of the past ?
There was no need for heat, or vacuum for electrons to flow
How can conductivity of conductors be explained with respect to energy bands ?
The valence band is partially filled or
Overlaps with conduction band
What happens when electrons jump into a higher energy level due to heat ?
Random motion for the electrons
What happens when it is due to an electric field ?
The electrons move in a direction opposite to the field
What is the nature of the valence and conduction band in insulators ?
Valence band - Completely filled
Conduction band - Completely empty
What is the order of the energy gap in between the valence and conduction band in insulators ?
What is the thermal energy possessed by an electron at a given temperature T ?
K is Boltzmann constant
Why do insulators not conduct electricity at room temperature ?
KT is very much below the band gap at room temperature
What is dielectric breakdown ?
The phenomenon that occurs when an insulator starts conducting electricity
How does this happen ?
By applying a sufficiently large voltage
What is the energy band gap in semi conductors ?
About 1 eV
What is the band gap for pure Silicon ?
What is the band gap for pure Germanium ?
What is doping ?
The process of adding a small amount of impurity to a semi conductor
Why is this done ?
To increase conductivity
What is the impurity called ?
What is an intrinsic conductor ?
A pure semiconductor
How does an intrinsic conductor conduct electricity ?
Thermal excitation only
What is an extrinsic conductor ?
A conductor, containing a small amount of impurity
What are the two types of extrinsic conductors ?
P - Type
What is the law of mass action ?
The product of charge carrier concentration remains constant
What kind of semiconductors does this apply to ?
Both extrinsic and intrinsic
Does the law of mass action vary with doping ?
No, the product remains the same even with variation in doping
When is Lorentz force experienced and by what ?
It is experienced by a moving charge when it is subjected to the influence of a magnetic field
What is hall effect ?
When a current carrying body is subjected to a perpendicular magnetic field, a mutually perpendicular electric field is induced
What are the applications of Hall Effect ?
Determination of charge carrier concentration, charge mobility