Three major characteristics of semiconductor

2018-08-28

1. Thermal properties

 

The resistivity of a semiconductor changes significantly with temperature. For example, pure helium, its resistivity is reduced to 1/2 of every tens of degrees of humidity. Subtle changes in temperature can be reflected in the apparent change in semiconductor resistivity. Using the thermal properties of the semiconductor, a temperature-sensitive component, thermistor, can be fabricated for use in temperature measurement and control systems. It is worth noting that various semiconductor devices have thermal properties that affect the stability of their operation when the ambient temperature changes.

 

2. Photosensitive properties

 

The resistivity of a semiconductor is very sensitive to changes in light. When there is light, the resistivity is small; when there is no light, the resistivity is large. For example, the commonly used cadmium sulfide photoresistor has a resistance of up to several tens of megaohms when there is no light. When exposed to light, the resistance drops to several tens of kilohms, and the resistance value changes by a thousand times. Using the photosensitive properties of semiconductors, various types of optoelectronic devices, such as photodiodes, phototransistors, and silicon photocells, are widely used in automatic control and radio technology.

 

3. Doping characteristics

 

In a pure semiconductor, the incorporation of a very small amount of impurity elements causes a great change in its resistivity. For example, in the pure silicon, the boron content of the parts per million is reduced from 214000 Ω·cm to 0.4 Ω·cm. That is, the conductivity of silicon is increased by more than 500,000 times. . It is precisely by incorporating certain specific impurity elements that artificially precisely control the conductivity of semiconductors to manufacture different types of semiconductor devices. It is no exaggeration to say that almost all semiconductor devices are made of semiconductor materials doped with specific impurities.


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