A semiconductor is a material whose electrical conductivity is between that of a conductor and an insulator. Its electrical properties are highly sensitive to temperature and the types and amounts of impurities it contains.
Semiconductors are the raw materials for manufacturing transistors. Their widespread application is primarily due to the significant variations in their resistivity under different conditions such as temperature, light exposure, and the type and concentration of impurities. Generally, the conductive properties of semiconductors exhibit the following three notable characteristics:
The resistivity of semiconductors decreases significantly as temperature increases, exhibiting a negative temperature coefficient. The conductivity of semiconductors enhances significantly with rising temperature; some semiconductors are particularly sensitive to temperature changes and are typically used to create thermal sensors.
The resistivity of semiconductors changes with varying light exposure. The conductivity of semiconductors varies with the intensity of light; for instance, cadmium sulfide films exhibit substantial changes when light intensity is high. In darkness, its resistance reaches tens of megaohms, behaving as an insulator; when exposed to light, its resistance drops to tens of kiloohms. This characteristic allows us to create various light-sensitive devices.
The resistivity of semiconductors is significantly influenced by the concentration of trace impurities. If trace amounts of other elements (commonly referred to as doping) are added to pure semiconductors, their conductivity will change significantly with varying doping concentrations. For example, adding one millionth of phosphorus to pure silicon changes its resistivity from ρ.14Ω·cm to 0.2Ω·cm. Various semiconductor devices (such as diodes, transistors, and field-effect transistors) are made utilizing these semiconductor characteristics.
From both technological and economic development perspectives, the importance of semiconductors is immense. Most electronic products, such as computers, mobile phones, or digital recorders, are closely related to semiconductors.
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Editor: Wang Yidi, Hao Jianni
Content Review: Liu Lianjun
Produced by the New Media Center of the College of Physics and Technology, Guangxi Normal University
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