In a semiconductor material, such as silicon or germanium, the movement of electrons plays a crucial role in its electrical behavior. At lower temperatures, the electrons are bound to their respective atoms and form stable bonds. However, as the temperature increases, the thermal energy provided to the semiconductor allows electrons to gain enough energy to break their bonds and move more freely within the material. This process can be explained using two main factors: increased thermal energy and the activation energy for bond breaking.
Increased Thermal Energy: When the temperature rises, the average kinetic energy of the atoms and electrons in the semiconductor also increases. This increased thermal energy causes the atoms to vibrate more vigorously, making the bonds between atoms weaker. As a result, some bonds break, and the electrons associated with those bonds become free to move.
Activation Energy: Breaking a bond requires a certain amount of energy called the activation energy. At lower temperatures, the thermal energy available is usually insufficient to provide the activation energy required for bond breaking. However, as the temperature increases, more electrons acquire energy equal to or greater than the activation energy, enabling them to break free from their bonds.
As a consequence of these factors, the number of broken bonds in a semiconductor increases as the temperature rises. The freed electrons are then available to participate in conduction, contributing to the semiconductor's electrical conductivity. At the same time, the formation of new bonds between atoms becomes less frequent as the increased thermal energy hampers the stabilization of new bonds. Thus, the number of formed bonds decreases with increasing temperature.
This relationship between temperature and the number of broken and formed bonds in a semiconductor has significant implications for its electrical behavior, including changes in conductivity, carrier concentration, and other properties.