Semiconductors Flashcards
At what temperature do atoms stop vibrating?
Absolute Zero
Describe the bands in an insulator
Full valence band, empty conduction band and a band gap
Describe the bands in a conductor
Full valence band, partly full conduction band and no band gap
Describe the bands in a semiconductor
Full valence band, empty conduction band and tiny band gap
What allows electrons to move in a semiconductor?
A voltage applied across it allows the electrons to move
Name some semiconductors
Silicon, germanium and selenium
What’s the difference between intrinsic and extrinsic semiconductors?
Extrinsic semiconductors have impurities added to them
What charge does an n-type semiconductor have?
Neutral
What charge does an p-type semiconductor have?
Neutral
What’s another name for ‘adding impurities’?
Doping
What type of hole does an p-type semiconductor have?
A Positive hole
What is the flow in an n-type caused by?
Negative electrons
What happens when you stick a p-type and n-type together?
You create a p-n junction
Describe a p-n junction
A negative p-type side and a positive n-type with a drift current from negative to positive
What’s the minimum voltage for a Forward biased diode (semiconductor) to work
0.7V in the opposite direction
What happens when electrons recombibe i in a diode?
They give out a photon
What happens when a high energy electron is absorbed?
An electron-hole pair is produced
Describe a photodiode
A p-type anode and an n-type cathode
Give a use of a reverse photodiode
A light sensor
What type of bias does a p-n junction have when the current flows from n-type to p-type?
Forward biased
How does a solar cell work?
A photon hits a p-n junction and splits to a p-type and n-type, creating a potential difference
Which bias does an LED have?
Forward
