Semiconductors And P-N Junctions

Question 1

Explain the structure of a conductor?

Answer 1

Conductors have:

1) Very low resistance
2) Conduction band is partially filled, leaving space for electrons to move into it from the valence band
3) There is no band gap

Question 2

Explain the structure of an insulator?

Answer 2

Insulators have:

1) A very high resistance
2) Valence band is full
3) Large band gap
4) Only electrons in the conduction band can move easily, there are none, so no conduction takes place

Question 3

Explain the structure of a semi-conductors?

Answer 3

Semi-conductors have:

1) A high resistance
2) Enough energy to move some electrons from the valence band to conduction band, to allow conduction to occur, at room temp
3) Small band gap

Question 4

What happens in an n-type semi conductor?

Answer 4

There is an extra electron that won’t be bonded into the valence band, instead the conduction band will have more electrons

Question 5

What happens in an p-type semi conductor?

Answer 5

There is a missing electron, which means more space above the valence bond

Question 6

Use ban theory to describe how LED’s emit light?

Answer 6

1) Voltage causes electrons to move towards the conduction band of the p-type.
2) Electrons drop from conduction band into valence band
3) Photon of light is emitted