Changes

===Positive Hole Theory===

===Positive Hole Theory===

The positive hole theory is that when an electron leaves its position in the lattice a positive hole is formed in its absence. This hole is then filled by another electron which in turn leaves a hole in its path which is filled by another electron and so on so forth. The apparant movement of "positive holes" mimicks the movement of positive charges, and hence semiconductors can be referred to as conducting by positive holes. This occurs in the valance band.

The positive hole theory is that when an electron leaves its position in the lattice a positive hole is formed in its absence. This hole is then filled by another electron which in turn leaves a hole in its path which is filled by another electron and so on so forth. The apparent movement of "positive holes" mimics the movement of positive charges, and hence semiconductors can be referred to as conducting by positive holes. This occurs in the valance band.

==Doping==

==Doping==

==Uses==

==Uses==

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 electric field which creates a "zone of exclusion". This zone of exclusion can be utilized 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.

[[Category: Technology]]

[[Category: Technology]]