Semiconductors

What Is A Semiconductor?• A semiconductor is a substance that has a

lower conductivity than a metal and a higher conductivity than a non-metal.

• They appear at the divide between metals and non-metals on the periodic table, for example silicone and Germanium.

• There are two types of semiconductor, p type and n type.

P type Semiconductors• P type semiconductors are made by

adding an atom with one less outer electron than the other atoms in the surrounding network.

• This means that the ‘impurity’ atom creates a hole where an electron would normally be, leaving room for electrons to move into allowing for electric current to flow.

N type Semiconductors• N type semiconductors are made by

adding an atom with one more outer electron than the other atoms in the surrounding network.

• This means that the ‘impurity’ atom supplies an extra electron to carry charge.

Conduc(k)tivity

• As a semiconductor’s heat increases so to does its electrical conductivity.

• Also a semiconductor’s conductivity increases with exposure to light.

Uses of the Semiconductor

• Can be used in photovoltaic cells, a vital component in solar cells.

• Commonly used to make electronic devices such as transistors, diodes and integrated circuits.

Questions From the Past

• The electrical conductivity of the semiconductor gallium arsenide increases on exposure to light.

• What name is given to this phenomenon?

• Answer: Photoconductivity

Another Question

• An example of a p-type semiconductor is• silicon doped with• A carbon• B arsenic• C aluminium• D phosphorus

• D is the answer.

End