The two main processes involved in the thermal diffusion of a semiconductor are:
Conduction: Conduction is the process of heat transfer within a solid material due to the movement of free electrons or vibrations of atoms or molecules. In semiconductors, heat is conducted through the lattice structure via phonons, which are quantized vibrations of the crystal lattice. When a temperature gradient exists within the semiconductor, phonons carry heat energy from regions of higher temperature to regions of lower temperature, resulting in thermal diffusion.
Carrier Diffusion: Carrier diffusion refers to the movement of charge carriers (electrons and holes) in response to a temperature gradient. In a semiconductor, carriers are influenced by both the thermal energy (which tends to make them move randomly) and an electric field (if present). When a temperature gradient is applied across a semiconductor, the carriers experience a net diffusion motion in the direction of decreasing temperature. This diffusion of carriers contributes to the overall thermal diffusion process.
In summary, during thermal diffusion in a semiconductor, heat is conducted through the lattice structure via phonons, while carrier diffusion causes the movement of charge carriers in response to the temperature gradient. Both processes contribute to the overall thermal conduction and diffusion of heat within the semiconductor material.