SEMICONDUCTORS
All materials can be classified into three major categories:
- Metals– materials that have a very high conductivity or low resistivity to current flow
- Insulators– materials that have a very poor conductivity
- Semiconductors– materials whose conductivity falls in between metals and insulators.
Semiconductors
Some examples of semiconductor materials are Germanium (Ge), Gallium Arsenide (GaAs) and Silicon (Si).
Semiconductor materials can broadly be classified into two typesโ intrinsic semiconductors and extrinsic semiconductors.
Intrinsic Semiconductors
Intrinsic semiconductors are those semiconductors, the electron concentration is equal to the hole concentration.
Extrinsic Semiconductors (n-type and p-type)
A semiconductor material that has been subjected to the doping process is called an extrinsic semiconductor.
Doping: It is the process of introduction of impurities into an intrinsic (undoped) semiconductor for the purpose of modulating its electrical, optical and structural properties.
By doping the extrinsic material can be made into two types of materials n-type and p-type. Both the n- and p-type materials are formed by adding a predetermined number of impurity atoms into a germanium or silicon base.
n-Type Material
The n-type is created by introducing those impurity elements that have five valence electrons (pentavalent), such as antimony, arsenic, and phosphorus.
p-Type Material
The p-type material is formed by doping a pure germanium or silicon crystal with impurity atoms having three valence electrons. The elements most frequently used for this purpose are boron, gallium, and indium.
