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Semiconductor refers to a material whose conductivity is between a conductor and an insulator at room temperature. Semiconductors are used in integrated circuits, consumer electronics, communication systems, photovoltaic power generation, lighting applications, and high-power power conversion.
Semiconductor refers to a material whose conductivity is between a conductor and an insulator at room temperature. Semiconductors are used in integrated circuits, consumer electronics, communication systems, photovoltaic power generation, lighting applications, and high-power power conversion. Diodes are devices made of semiconductors. From the perspective of technology or economic development, the importance of semiconductors is great. The core units of most electronic products today, such as computers, mobile phones, or digital recorders, are very closely related to semiconductors. Common semiconductor materials are silicon, germanium, gallium arsenide, etc., and silicon is one of the most influential semiconductor materials in commercial applications.
There are many forms of matter, solid, liquid, gas, plasma, and so on. We usually refer to materials with poor conductivity, such as coal, artificial crystals, amber, ceramics, etc. as insulators. And conductive metals such as gold, silver, copper, iron, tin, aluminum, etc. are called conductors. The material between the conductor and the insulator can be simply called a semiconductor. Until the 1930s, material purification technology has improved, the existence of semiconductors was truly recognized by the academic community. From the perspective of science and technology and economic development, semiconductors affect people's daily work and life.
silicon
The discovery of semiconductors actually goes back a long time.
In 1833, Faraday, the father of British scientist electronics, first discovered that the resistance of silver sulfide with temperature changes is different from that of ordinary metals. Generally, the resistance of a metal increases with temperature, but Faraday found the resistance of silver sulfide materials. It decreases as the temperature rises. This is the first discovery of a semiconductor phenomenon.
In 1839, Berclair in France discovered that the junction formed by the contact between the semiconductor and the electrolyte will generate a voltage under the light. This is the photovoltaic effect known later, which is the second characteristic of the discovered semiconductor.
In 1873, Smith of the United Kingdom discovered the photoconductance effect that the conductance of selenium crystal material increased under light, which is the third characteristic of semiconductors.
In 1874, Braun of Germany observed that the conductance of certain sulfides was related to the direction of the applied electric field, that is, its conductivity was directional. A forward voltage was applied across it, and it was conducting; if reversing the polarity of the voltage, it does not conduct electricity. This is the rectifying effect of the semiconductor, and it is also the fourth characteristic peculiar to the semiconductor. In the same year, Schuster discovered the rectifying effect of copper and copper oxide.
Although these four characteristics of semiconductors were discovered before 1880, the term semiconductor was first used by Cowney Berg and Weiss only in 1911. It was concluded that these four characteristics of semiconductors were not completed by Bell Labs until December 1947.
In October 2019, an international scientific research team claimed that compared with only 3 parameters obtained in traditional Hall measurement, the new technology can obtain up to 7 parameters at each test light intensity: including the mobility of electrons and holes; charger density under light, recombination lifetime, diffusion length for electron, hole, and bipolar types.
Elemental semiconductors refer to semiconductors made of a single element, of which the research on silicon and tin was earlier. It is a solid material with semiconducting properties composed of the same elements, which are easily affected by trace impurities and external conditions. At present, only silicon and germanium have good performance and are widely used. Selenium is used in the fields of electronic lighting and optoelectronics. Silicon is widely used in the semiconductor industry, which is mainly affected by silicon dioxide. It can form a mask on device manufacturing, can improve the stability of semiconductor devices, and is conducive to automated industrial production.
Single-crystal germanium wafer
Inorganic composites are mainly composed of single-element semiconductor materials. Of course, there are also semiconductor materials composed of multiple elements. The main semiconductor properties are the group I and groups V, VI, and VII; group II and groups IV, V, VI, and VII; Group III and Group V, VI; Groups IV and IV, VI; Groups V and VI; Groups VI and VI. But affected by the characteristics and manufacturing methods of the elements, not all compounds are compatible with semiconductor materials requirements. This semiconductor is mainly used in high-speed devices. InP's transistors are faster than other materials. They are mainly used in optoelectronic integrated circuits and nuclear radiation-resistant devices. For materials with high electrical conductivity, it is mainly used in LED and other aspects.
Organic compounds refer to compounds containing carbon bonds in the molecule. The organic compounds and the carbon bonds are perpendicular to each other to form a conduction band. Through chemical addition, they can be brought into the energy band. This can lead to electrical conductivity and thus form an organic compound semiconductor. Compared with conventional semiconductors, this semiconductor has the characteristics of low cost, good solubility, and easy processing of materials. The conductive properties can be controlled by controlling molecules, which have a wide range of applications and are mainly used in organic thin films and organic lighting.
It is also called amorphous semiconductor or glass semiconductor, which belongs to a class of semi-conductive materials. Amorphous semiconductors, like other amorphous materials, have short-range ordered and long-range disordered structures. It mainly forms the amorphous silicon by changing the relative positions of the atoms and changing the original periodic arrangement. The crystalline state and the amorphous state are mainly different from whether the atomic arrangement has a long program. It is difficult to control the performance of amorphous semiconductors. With the invention of technology, amorphous semiconductors have begun to be used. This manufacturing process is simple, mainly used in engineering, and has a good effect on light absorption. It is mainly used in solar cells and liquid crystal displays.
A semiconductor that contains no impurities and no lattice defects is called an intrinsic semiconductor. At extremely low temperatures, the valence band of a semiconductor is full. After being thermally excited, some electrons in the valence band will pass the forbidden band and enter the empty band with higher energy. The presence of electrons in the empty band will become the conduction band. The absence of an electron forms a positively charged vacancy called a hole. Hole conduction is not actual motion, but an equivalent. When electrons conduct electricity, holes of the same amount of electricity move in the opposite direction. They generate directional motion under the action of an external electric field to form a macroscopic current, which is called electron conduction and hole conduction, respectively. This type of hybrid conduction is called intrinsic conduction due to the generation of electron-hole pairs. The electrons in the conduction band fall into holes, and the electron-hole pairs disappear, which is called recombination. The energy released during recombination will become electromagnetic radiation (luminescence) or thermal vibrational energy (heat) of the lattice. At a certain temperature, the generation and recombination of electron-hole pairs coexist and reach dynamic equilibrium. At this time, the semiconductor has a certain carrier density and thus a certain resistivity. As the temperature increases, more electron-hole pairs are generated, the carrier density increases and the resistivity decreases. The resistivity of pure semiconductors without lattice defects is large, and there are not many practical applications.
Semiconductors are used in integrated circuits, consumer electronics, communication systems, photovoltaic power generation, lighting applications, and high-power power conversion, etc.
The photovoltaic effect of semiconductor materials is the basic principle of solar cell operation. At this stage, the photovoltaic application of semiconductor materials has become a hot topic, and it is the fastest growing and best developing clean energy market in the world. The main manufacturing material of solar cells is semiconductor materials. The main criterion for judging the quality of solar cells is the photoelectric conversion rate. The higher the photoelectric conversion rate, the higher the efficiency of the solar cell. According to the different semiconductor materials used, solar cells are divided into crystalline silicon solar cells, thin-film cells, and III-V compound cells.
LED is a semiconductor light-emitting diode built on a semiconductor transistor. Using LED technology, the semiconductor light source is small in size. It can achieve flat packaging, low heat generation during work, energy-saving and high efficiency, long product life, fast response time, and environmental protection without pollution. Once it came out, it quickly became popular and became a new generation of high-quality lighting sources. It has been widely used in our lives such as traffic lights, backlights for electronic products, landscaping light sources for urban nightscapes, and indoor lighting.
LED
The mutual conversion of alternating current and direct current is very important for the use of electrical appliances and is a necessary protection for electrical appliances. This requires waiting for a power conversion device. Silicon carbide has a high breakdown voltage strength, wide forbidden bandwidth, and high thermal conductivity. Therefore, SiC semiconductor devices are very suitable for applications with the high power density and high switching frequency. Power supply replacement devices are one of them. Another performance of silicon carbide components in high temperature, high pressure, and high frequency has now been widely used in deep well drilling, inverters for power generation equipment, energy converters for electric hybrid vehicles, power conversion for light rail trains, and other fields. Due to the advantages of SiC itself and the industry's need for lightweight and high conversion efficiency semiconductor materials at the current stage, SiC will replace Si and become the most widely used semiconductor material.
Semiconductor refrigeration technology is widely used in current refrigeration technology. During the growth of crops in greenhouses, semiconductor refrigeration technology can effectively control the environmental temperature, especially some plants that have high requirements on the environment. Using semiconductor refrigeration technology to shape the growth environment can promote plant growth. Semiconductor refrigeration technology is reversible and can be used for cooling or heating, and it has a good effect on the adjustment of ambient temperature.
The application principle of semiconductor refrigeration technology is based on the Peltier principle. In 1834, French scientist Peltier discovered the role of semiconductor refrigeration. The Peltier principle is also known as the "Peltier benefit", which is to make full use of two different conductors. Use a circuit composed of A and B to apply direct current. At the joints of the circuit, Joule heat can be generated at the same time. There will also be some other heat released, and at this time it will be found that the other joint is not releasing heat, but is absorbing heat. This phenomenon is reversible. As long as the direction of the current is changed, the exothermic and endothermic operations can be adjusted. There is a proportional relationship between the intensity of the current and the absorbed and emitted heat, which is related to the characteristics of the semiconductor itself. Because the Peltier effect of metal materials is relatively weak, and the operation of semiconductor materials based on the Peltier principle will produce stronger effects, semiconductors have become the main raw material in refrigerated materials. However, for the use of this material, it should be noted that the dimensionless value of most semiconductor materials is close to 1, which is lower than the solid theoretical model. The result obtained in the calculation of actual data is 4. So for semiconductor materials in the application, in order to make the rational use of semiconductor refrigeration technology, an in-depth research is required.
Semiconductor refrigerator
Semiconductor refrigeration technology has been widely used in the field of medicine and in the industrial field, even in daily life, so this technology has a very promising development prospect. For example, the use of conductor cooling technology in modern refrigeration equipment, such as refrigerators, air conditioners, etc., can be equipped with electronic coolers. Semiconductor refrigerators use semiconductor refrigeration technology.
Different numbers of semiconductor refrigeration chips can be connected in parallel or in series according to the needs during the connection process, and they can be put into place to play a role. In the 1950s, the former Soviet Union developed a small model refrigerator with a capacity of only 10 liters. The refrigerator is very small and easy to use. Japan has developed a refrigerator that is designed to store red wine. For the temperature to be strictly controlled, the application of semiconductor refrigeration technology can meet the refrigeration requirements of refrigerators. With the continuous development of society, people are increasingly demanding refrigeration equipment while pursuing a quality of life. When people use semiconductor refrigerators, they will find that this type of refrigerator consumes less power than traditional refrigerators, and can even reach 20%, which has a good energy-saving effect.
The semiconductor air conditioner is different from the air conditioner used in daily life but is used in special places, such as cabins, submarines, and so on. The use of relatively stable refrigeration technology can not only ensure rapid cooling but also meet the requirements of semiconductor refrigeration technology. Some American companies have found that semiconductor refrigeration technology also has an important function, which is to rationally apply it to active batteries, which can ensure continuous power supply, which can exceed 8 hours. Semiconductor refrigeration technology is also applied in automotive refrigeration equipment, including agriculture, astronomy and medicine, and semiconductor refrigeration technology.
(1) Difficulties of semiconductor refrigeration technology
Many parameters are involved in the process of semiconductor refrigeration, and the conditions are complex and changeable. Either parameter will affect the cooling effect. In laboratory research, because it is difficult to meet the specified noise, it is necessary to study the laboratory environment, but the discussion of some influencing factors is difficult. Semiconductor refrigeration technology is a refrigeration technology based on the particle effect, which is reversible. Therefore, in the application of refrigeration technology, there will be a large temperature difference between the hot and cold ends, which will inevitably affect the cooling effect.
(2) Problems in semiconductor refrigeration technology
First, the quality coefficient of semiconductor materials cannot be further improved as required, which will inevitably affect the application of semiconductor refrigeration technology. Secondly, the cold-end cooling system and the hot-end cooling system are optimized and designed, but they have not been upgraded in technology and are still in the theoretical stage. Third, semiconductor refrigeration technology has limitations for applications in other fields and related fields. Therefore, semiconductor refrigeration technology is rarely used, and research on semiconductor refrigeration technology is difficult to expand technically from the perspective of the application. Fourth, in the market economy environment, the development of science and technology, and the development of semiconductor refrigeration technology, need to consider many aspects of problems.
GaN charger
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 have shown a rapid development trend. Among GaN-based optoelectronic devices, a blue light-emitting diode was the first to achieve commercial production. After the successful development of blue-light LEDs and LDs, the research direction shifted to GaN ultraviolet photodetectors. GaN materials also have a considerable application market in microwave power. GaN semiconductor switches are hailed as a new milestone in semiconductor chip design. Scientists at the University of Florida have developed an important device that can be used to make new types of electronic switches that can provide a smooth, uninterrupted power supply.
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