The Fermi surface is a theoretical construct in solid-state physics that represents the boundary in momentum space between filled and unfilled energy levels for a given electron system. It is named after physicist Enrico Fermi.
In semiconductors, the Fermi surface plays a crucial role in determining the electrical and thermal properties of the material. It is a key factor in understanding the electronic band structure and the behavior of charge carriers in semiconductors.
The Fermi surface can be observed through various techniques, such as angle-resolved photoemission spectroscopy and de Haas-van Alphen effect. These methods involve measuring the interactions between electrons and an external magnetic field to determine the shape and size of the Fermi surface.
The Fermi surface is directly related to the size of the band gap in semiconductors. In an insulator, the Fermi level lies within the band gap, which means there are no available energy states for the electrons to occupy. In contrast, in a semiconductor, the Fermi level lies closer to the conduction band, allowing for the movement of charge carriers.
The knowledge of the Fermi surface has greatly influenced the development of semiconductor technology. The ability to manipulate the Fermi surface through doping and other techniques has allowed for the creation of various semiconductor devices, such as transistors and diodes, which are essential components in modern electronic devices.