Semiconductor Physics Flashcards
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 ?
5 eV
What is the thermal energy possessed by an electron at a given temperature T ?
KT,
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 ?
1.1 eV
What is the band gap for pure Germanium ?
0.72 eV
What is doping ?
The process of adding a small amount of impurity to a semi conductor
Why is this done ?
To increase conductivity
