Introduction to the role, classification and characteristics of semiconductors
Published time: 2019-08-05
A semiconductor refers to a material whose electrical conductivity is between a conductor and an insulator at normal temperature. Semiconductors have a wide range of applications in radios, televisions, and temperature measurement. For example, a diode is a device fabricated using semiconductors. A semiconductor is a material that is electrically controllable and can range from insulator to conductor. From the perspective of technology or economic development, the importance of semiconductors is enormous. Most of today's electronic products, such as computers, mobile phones or digital recorders, have a very close relationship with semiconductors. Common semiconductor materials are silicon, germanium, gallium arsenide, etc., and silicon is one of the most influential in commercial applications.
There are many semiconductor materials, which can be divided into elemental semiconductors and compound semiconductors according to their chemical composition. Silicon and silicon are the most commonly used elemental semiconductors; compound semiconductors include Group III and V compounds (gallium arsenide, gallium phosphide, etc.), Group II and VI compounds (cadmium sulfide, zinc sulfide, etc.), oxides ( An oxide of manganese, chromium, iron, or copper), and a solid solution composed of a group III-V compound and a group II-VI compound (gallium aluminum arsenide, gallium arsenide phosphorus, etc.). In addition to the above crystalline semiconductor, there are amorphous glass semiconductors, organic semiconductors, and the like.
Semiconductor classification, according to its manufacturing technology can be divided into: integrated circuit devices, discrete devices, optoelectronic semiconductors, logic ICs, analog ICs, storage and other large categories, in general these will be divided into small categories. In addition, it is classified by application fields, design methods, etc., and is not commonly used, but is classified according to IC, LSI, VLSI (super LSI) and its scale. In addition, according to the signals it processes, it can be divided into analog, digital, analog digital mixing and function classification methods.
The role and value of semiconductors
Currently widely used semiconductor materials are germanium, silicon, selenium, gallium arsenide, gallium phosphide, indium antimonide, etc. Among them, the production technology of germanium and silicon materials is relatively mature and used more.
Components made of semiconductor materials, integrated circuits, and the like are important basic products of the electronics industry and have been widely used in various aspects of electronic technology. The production and research of semiconductor materials, devices, and integrated circuits has become an important part of the electronics industry. In terms of new product development and new technology development, the more important areas are:
(1) Integrated Circuits It is one of the most active areas in the development of semiconductor technology and has evolved into a stage of large-scale integration. With tens of thousands of transistors on a few square millimeters of silicon, a micro-information processor can be fabricated on a single piece of silicon, or other more complex circuit functions can be accomplished. The development direction of integrated circuits is to achieve higher integration and micro power consumption, and to achieve information processing speeds of picoseconds.
(2) Microwave devices Semiconductor microwave devices include receiving, controlling, and transmitting devices. Receiver devices below the millimeter band have been widely used. In the centimeter band, the power of the transmitting device has reached several watts, and people are getting more output power by developing new devices and developing new technologies.
(3) Optoelectronic devices The development of semiconductor light-emitting devices, imaging devices and laser devices has made optoelectronic devices an important field. Their application range is mainly: optical communication, digital display, image reception, optical integration and so on.
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 in the absence of illumination. When exposed to light, the resistance drops to tens of kilohms at a time, and the resistance value changes by a thousand times. Using the photosensitive properties of semiconductors, vFarious 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, blending in pure silicon. The boron content of a million parts 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.
Future development of semiconductors
The development of third-generation semiconductor materials and devices represented by GaN (gallium nitride) is the core and foundation of the emerging semiconductor industry, and its research and development is showing a trend of rapid development. Among GaN-based optoelectronic devices, blue LEDs are the first to achieve commercial production. After the successful development of blue LEDs and LDs, the research direction has shifted to GaN UV detectors. GaN materials also have a considerable application market in terms of microwave power. GaN semiconductor switches are hailed as a new milestone in the design of semiconductor chips. Scientists at the University of Florida have developed an important device that can be used to make new electronic switches that provide a smooth, uninterruptible power supply.
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