A semiconductor is a material that has a conductivity somewhere between extremes of an insulator and a conductor. e.g.:- Ge and Si. An increase in temperature of a semiconductor can result in a substantial increase in the number of free electrons in the material. Semiconductor material such as Ge and Si that show a reduction in resistance with increase in temperature are said to be have a negative temperature co-efficient.
Energy band diagram
Here EG represents the energy band gap. It is the amount of energy that should be imparted to the electron in the valence conduction bond.
The characteristics of semiconductor materials can be altered significantly by the addition of certain impurity atoms into the relatively pure semiconductor material by doping process. A semiconductor material that has been subjected to the doping process is called as extrinsic material. Pure semiconductor material without any impurity is known as an intrinsic semiconductor material.
n - type material
The n - type is created by introducing impurity elements that are penta-valent such as Antimony, Arsenic and Phosphorous. These diffused impurities are called donor atoms.
p - type material
The p - type material is formed by doping impurity elements that are tri-valent such as Boron, Gallium and Indium. These diffused impurities are called acceptor atoms.