Pure Semiconducting Materials

Elemental Composition and Crystal Structure

Describes materials composed of a single element, such as silicon (Si) or germanium (Ge), exhibiting semiconducting properties. Typically, these materials possess a highly ordered crystalline structure, such as a diamond cubic lattice.

Electronic Band Structure

Explanation of the electronic band structure, featuring a valence band (where electrons reside at absolute zero) and a conduction band (where electrons can freely move and conduct electricity). A crucial aspect is the energy gap, or bandgap, separating the valence and conduction bands. The magnitude of this gap determines the semiconducting characteristics.

Carrier Concentration

In an ideal pure semiconducting material at absolute zero, there are no free charge carriers (electrons or holes). At temperatures above absolute zero, thermal excitation causes electrons to jump from the valence band to the conduction band, creating electron-hole pairs. The concentration of electrons in the conduction band is equal to the concentration of holes in the valence band. This concentration is temperature-dependent.

Intrinsic Carrier Concentration (n_i)

Defines the density of electrons and holes present in the pure material under thermal equilibrium. This quantity is highly dependent on temperature and the material's bandgap.

Electrical Conductivity

The material's ability to conduct electricity is determined by the concentration and mobility of charge carriers. The electrical conductivity is directly proportional to both the electron and hole concentrations and their respective mobilities.

Temperature Dependence

The conductivity of a pure semiconducting material increases exponentially with increasing temperature. This is because more electrons are thermally excited into the conduction band at higher temperatures, leading to a higher carrier concentration.

Applications

Serve as a foundational base for understanding doped semiconductors. Their behavior is critical in developing and understanding the behaviour of transistors and other electronic devices. While not typically used directly in devices, analysis of them provides crucial insights for optimizing the properties of doped materials.