Changes

A semiconductor is a conductor whose resistance decreases with increased temperature. Superconductors consist of a lattice of a group four element, typically [[silicon]] or [[germanium]]. The [[electrons]] that cause current flow are bound in the lattice, with on average 1 free electron per 250,000 atoms. When energy (usually heat) is supplied to the conductor electrons are freed from the lattice and conduction occurs. More energy increases the number of free electrons up to a point where the substance loses its conductivity.

A '''semiconductor''' is a conductor whose resistance decreases with increased temperature. Superconductors consist of a lattice of a group four element, typically [[silicon]] or [[germanium]]. The [[electrons]] that cause current flow are bound in the lattice, with on average 1 free electron per 250,000 atoms. When energy (usually heat) is supplied to the conductor electrons are freed from the lattice and conduction occurs. More energy increases the number of free electrons up to a point where the substance loses its conductivity.

==Band Theory==

==Band Theory==

Semiconductors are not used to replace ordinary conductors, given that their resistance remains significantly higher at all temperatures. However, their unique properties can be exploited by creating a n-p junction, when an n-type and a p-type semiconductor are placed together. The electrons in the conduction band of the n-type substance fill up some of the positive holes in the p-type conduction, producing a negative charge on the p-type side and hence an electic field which creates a "zone of exclusion". This zone of exclusion can be utilised in many instances, including in solid state devices acting as diodes (ensuring direction of current in one direction only) and triodes (increasing the current flowing through a circuit) and in solar cells. The former of these has replaced transistor valves in appliances such as radios and photocells.

Semiconductors are not used to replace ordinary conductors, given that their resistance remains significantly higher at all temperatures. However, their unique properties can be exploited by creating a n-p junction, when an n-type and a p-type semiconductor are placed together. The electrons in the conduction band of the n-type substance fill up some of the positive holes in the p-type conduction, producing a negative charge on the p-type side and hence an electic field which creates a "zone of exclusion". This zone of exclusion can be utilised in many instances, including in solid state devices acting as diodes (ensuring direction of current in one direction only) and triodes (increasing the current flowing through a circuit) and in solar cells. The former of these has replaced transistor valves in appliances such as radios and photocells.