Electrical conductivity refers to the ease with which electrical current can flow through a material. It is an important characteristic of a material. Conductors are those materials that allow the current to pass through them, while insulators are those that do not allow current to flow through them. On the other hand, there are materials that act as conductors and insulators when the flow of current through them is taken as a relative parameter. Such materials are called semiconductors. Here we explain the temperature coefficients of semiconductors in electronics.
What is Resistivity?
Resistivity is an intrinsic property of any substance. It means that it is a constant value for the substance with respect to a specific temperature. Resistivity of a substance is the resistance of a material of unit cross-sectional area and unit length.
What is Temperature Coefficient?
Temperature Coefficient, or TC, is that property of certain materials by which their physical value changes due to direct changes in their body or indirectly due to ambient temperature around them. In other words, as a material or component gets hotter (or colder), its value changes quite considerably and therefore is not constant all the time at all temperatures. When we take to understand how much a material’s resistance increases or decreases according to its temperature change, we use the temperature coefficient of resistance, α (Greek letter alpha), for that purpose.
Temperature Dependence
With an increase in temperature, the energy gap in semiconductors between their conduction band and valence band goes down exponentially. The valence electrons in a semiconductor gain sufficient energy at a high temperature to break the covalent bond and jump to the conduction band. Thus, at very high temperatures, more charge carriers are produced, thereby decreasing the resistivity of the semiconductor. The semiconductor thus has a decreased resistivity as temperature rises, leading to its increased conductivity. A semiconductor possesses excellent conductivity at very high temperatures.
The semiconductor material has a negative temperature coefficient of resistance. The resistance of the semiconductor substances decreases with an increase in temperature. The resistivity of the semiconductor decreases exponentially with an increase in temperature.
Advantages
Temperature coefficient of resistance is what makes the semiconductor electronics of today possible.
Platinum Resistance Thermometers (PRTs): Widely used for industrial temperature measurements due to platinum’s predictable resistance changes, PRTs are ideal for high-temperature applications where accuracy and stability are required.
Thermistors in HVAC Systems: Used in everyday applications such as HVAC systems, car engines and home appliances, thermistors provide a practical solution for temperature sensing. These semiconductor devices exhibit large resistance changes with relatively small temperature variations, making them both sensitive and accurate.
Bolometers in Infrared Detection: Common in infrared detection, bolometers use resistance changes caused by temperature shifts to measure radiation. By detecting heat, they provide critical information in fields such as astronomy and environmental monitoring. Companies like Google use cooling solutions, such as synthetic jet cooling, to maintain server performance under heavy loads.
The concept of Temperature Coefficients of Semiconductors significantly impacts everyday technologies and specialized industrial applications. Understanding how negative temperature coefficient sensors work and where to apply them helps electronics designers and thermal managers optimize their systems.
