What is the Difference Between Electron Rich and Electron Deficient Impurities

The key difference between electron rich and electron deficient impurities is that electron rich impurities are doped with group 1s elements such as P and As, which consist of 5 valence electrons, whereas electron-deficient impurities are doped with group 13 elements such as B and Al, which of 3 valence electrons.

The terms electron-rich and electron-deficient impurities come under semiconductor technology. Semiconductors usually behave in two ways: intrinsic conduction and extrinsic conduction. In intrinsic conduction, when electricity is provided, the electrons move behind a positive charge or hole at the site of a missing electron because pure silicon and germanium are poor conductors having a network of strong covalent bonds. This makes the crystal conduct electricity. In extrinsic conduction, the conductivity of intrinsic conductors is increased by the addition of an appropriate amount of suitable impurity. We call this process “doping.” The two types of doping methods are electron-rich and electron-deficient doping.

1. Overview and Key Difference
2. What are Electron Rich Impurities
3. What are Electron Deficient Impurities
4. Electron Rich vs Electron Deficient Impurities in Tabular Form
5. Summary – Electron Rich vs Electron Deficient Impurities

What are Electron Rich Impurities?

Electron-rich impurities are types of atoms having more electrons that are useful in increasing the conductivity of semiconductor material. These are named as n-type semiconductors because the number of electrons is increased during this doping technique.

In this type of semiconductor, atoms with five valence electrons are added to the semiconductor, which results in four out of five electrons being used in the formation of four covalent bonds with four neighboring silicon atoms. Then the fifth electron exists as an extra electron, and it becomes delocalized. There are many delocalized electrons that can increase the conductivity of doped silicon, thereby increasing the conductivity of the semiconductor.

What are Electron Deficient Impurities?

Electron-rich impurities are types of atoms having fewer electrons, which is useful in increasing the conductivity of semiconductor material. These are named as p-type semiconductors because the number of holes is increased during this doping technique.

In this type of semiconductor, an atom with three valence electrons is added to the semiconductor material, replacing the silicon or germanium atoms with the impurity atom. Impurity atoms have valence electrons that can make bonds with three other atoms, but then the fourth atom remains free in the crystal of silicon or germanium. Therefore, this atom is now available for conducting electricity.

What is the Difference Between Electron Rich and Electron Deficient Impurities?

The key difference between electron rich and electron deficient impurities is that electron rich impurities are doped with group 1s elements such as P and As that contain 5 valence electrons, whereas electron deficient impurities are doped with group 13 elements such as B and Al that contain 3 valence electrons. When considering the role of impurity atoms, in electron rich impurities, 4 out of 5 electrons in the impurity atom are used in forming covalent bonds with 4 neighboring silicon atoms, and the 5^th electron remains extra and becomes delocalized; however, in electron deficient impurities, the 4^th electron of the lattice atom remains extra and isolated, which can create an electron hole or electron vacancy.

The following table summarizes the difference between electron rich and electron deficient impurities.

Summary – Electron Rich vs Electron Deficient Impurities

Semiconductors are solids having the properties intermediate between metals and insulators. These solids have only a small difference in energy between the filled valence band and empty conduction band. Electron rich impurities and electron deficient impurities are two terms we use to describe semiconductor materials. The key difference between electron rich and electron deficient impurities is that electron rich impurities are doped with group 1s elements such as P and As that contains 5 valence electrons, whereas electron-deficient impurities are doped with group 13 elements such as B and Al that contains 3 valence electrons.