Semiconductor vs. Semimetal — What's the Difference?

Semiconductors are materials whose electrical conductivity can be precisely controlled through doping and environmental changes, making them fundamental to electronic devices like transistors and diodes. They have a bandgap that allows them to act as insulators at zero Kelvin but conduct electricity when energy is applied. On the other hand, semimetals possess a small overlap between the valence band and the conduction band, granting them conductive properties without the need for external energy. This overlap results in their unique position on the metal-nonmetal spectrum, often leading to unusual electronic and thermal properties.

The practical applications of semiconductors are vast and varied, ranging from microelectronic circuits to solar cells. Their ability to switch between conducting and insulating states underlies the operation of most modern electronics. Semimetals, whereas, find their niche in applications that benefit from their mixed properties, like certain types of sensors, thermoelectric devices, and in quantum computing as materials that may host exotic states of matter.

The behavior of semiconductors is highly temperature-dependent; increasing temperature generally increases their conductivity by providing energy to bridge the bandgap. Semimetals, however, demonstrate less dramatic changes in conductivity with temperature, owing to their small but non-zero band overlap, which makes their conductive properties less sensitive to temperature variations.

From a technological perspective, the development of semiconductors has been a cornerstone of the digital age, enabling the miniaturization and efficiency of electronic components. Semimetals, on the other hand, are explored for their potential in next-generation electronic, magnetic, and thermoelectric applications, highlighting the ongoing research into their novel physical phenomena.

The distinction between semiconductors and semimetals also extends to their electronic band structure, which fundamentally influences their electrical behavior. Semiconductors have a clear bandgap separating the valence and conduction bands, while semimetals have bands that slightly overlap, allowing electrons to move more freely at low energies.