Semiconductors have three main characteristics:
1. Thermal sensitivity characteristics
The resistivity of semiconductors changes significantly with temperature. For example, pure germanium, for every 10 degrees increase in humidity, its electrical resistivity decreases to 1/2 of its original value. The subtle changes in temperature can be reflected in the significant changes in semiconductor resistivity. By utilizing the thermal sensitivity of semiconductors, temperature sensing elements - thermistors - can be made for use in temperature measurement and control systems.
It is worth noting that various semiconductor devices have thermal sensitivity, which affects their stability when the ambient temperature changes.
2. Photosensitive characteristics
The resistivity of semiconductors is highly sensitive to changes in light. When illuminated, the electrical resistivity is very low; When there is no light, the electrical resistivity is high. For example, the commonly used cadmium sulfide photoresistor has a resistance of several tens of megaohms in the absence of light, when exposed to light. The resistance suddenly dropped to tens of thousands of ohms, and the resistance value changed thousands of times. By utilizing the photosensitive properties of semiconductors, various types of optoelectronic devices are produced, such as photodiodes, phototransistors, and silicon photocells. Widely used in automatic control and radio technology.
3. Doping characteristics
In pure semiconductors, doping extremely small amounts of impurity elements can cause a significant change in their electrical resistivity. For example. Doping in pure silicon. The resistivity of boron element, which is less than 214000 Ω· cm, will decrease to 0.4 Ω· cm, which means that the conductivity of silicon will increase by more than 500000 times. People precisely control the conductivity of semiconductors by doping certain specific impurity elements, and manufacture different types of semiconductor devices. It can be said without exaggeration that almost all semiconductor devices are made of semiconductor materials doped with specific impurities.
