Polarisation in Semiconductors

In semiconductors, the type of polarisation that exists is interfacial or space charge polarisation. This type of polarisation occurs at the interface between different materials or at the boundaries within a semiconductor material. It is primarily caused by the presence of charged particles and their redistribution in response to an applied electric field.

Interfacial or Space Charge Polarisation

Interfacial or space charge polarisation arises due to the accumulation of charges at the boundaries or interfaces within a semiconductor material. When an electric field is applied to a semiconductor, the charge carriers (electrons and holes) present in the material experience a force and redistribute themselves.

Key Points:
- The redistribution of charge carriers leads to the formation of a space charge region near the interfaces or boundaries of the semiconductor.
- This space charge region consists of fixed positive and negative charges, which create an electric field opposing the applied field.
- The presence of this space charge region affects the overall polarisation behavior of the semiconductor.
- The interfacial or space charge polarisation is particularly significant in devices such as pn junctions, MOS capacitors, and Schottky diodes, where the interface between different materials plays a crucial role.

Other Types of Polarisation

While interfacial or space charge polarisation is the dominant type of polarisation in semiconductors, it is essential to understand the other types of polarisation as well.

Electronic Polarisation: This type of polarisation occurs in materials with covalent or metallic bonding. It arises due to the displacement of electrons within the atomic or molecular structure of the material, leading to the creation of an induced dipole moment.

Ionic Polarisation: Ionic polarisation occurs in materials with ionic bonding, such as crystals with positive and negative ions. It arises due to the displacement of positive and negative charges within the material, resulting in the formation of induced dipoles.

Orientational Polarisation: This type of polarisation occurs in polar molecules, where the permanent dipole moments align in response to an applied electric field.

Conclusion

In summary, the type of polarisation that exists in semiconductors is interfacial or space charge polarisation. This polarisation arises due to the accumulation of charges at the interfaces or boundaries within the semiconductor material. While other types of polarisation, such as electronic, ionic, and orientational, are present in different materials, they are not the primary mechanisms responsible for polarisation in semiconductors.