1. Intrinsic Semiconductors:
* At low temperatures:
* Few electrons have enough energy to break free from their covalent bonds and become conduction electrons.
* Conductivity is very low.
* As temperature increases:
* More electrons gain enough thermal energy to break free, increasing the number of free charge carriers.
* Conductivity increases exponentially.
* At very high temperatures:
* The number of electron-hole pairs becomes so high that the semiconductor starts behaving like a metal.
2. Extrinsic Semiconductors:
* Doped semiconductors (n-type or p-type) have a higher conductivity than intrinsic semiconductors at room temperature due to the presence of impurities.
* Temperature effects on conductivity:
* Low temperatures: Conductivity is mainly due to the dopant atoms.
* Moderate temperatures: Conductivity increases with temperature as more electrons (n-type) or holes (p-type) become available for conduction.
* High temperatures: Intrinsic carriers start to dominate as their number increases exponentially, eventually exceeding the dopant concentration. This leads to a decrease in conductivity as the material becomes more like an intrinsic semiconductor.
Overall, the conductivity of a semiconductor increases with temperature up to a certain point, and then starts to decrease.
Factors affecting the variation:
* Type of semiconductor: Intrinsic vs. extrinsic, doping concentration, and type of dopant.
* Temperature range: The behavior is different at different temperatures.
Applications of temperature dependence:
* Thermistors: Semiconductor devices used for temperature sensing.
* Temperature-sensitive circuits: Used in various applications like controlling motor speed, alarm systems, etc.
In summary, the electrical conductivity of a semiconductor increases with temperature due to the increase in the number of free charge carriers. However, at high temperatures, the effect of intrinsic carriers becomes dominant, leading to a decrease in conductivity.
