From the perspective of science and technology or economic development, the importance of semiconductors is very great.Most electronic products, such as computers, mobile phones or digital recorders, are closely related to semiconductors.
Matter exists in various forms, including solid, liquid, gasPlasmawait.We usuallyConductivityPoor materials, such as coalIntraocular lens, amber, ceramics, etcinsulator。The metals with good conductivity, such as gold, silver, copper, iron, tin, aluminum, are called conductors.Materials between conductors and insulators can be simply called semiconductors.Compared with conductors and insulators, the discovery of semiconductor materials was the latest. It was not until the 1930s, when the purification technology of materials was improved, that the existence of semiconductors was truly recognized by the academic community.[1]
Semiconductors refer to materials with conductivity between conductors and insulators at room temperature.Semiconductor refers to a material with controllable conductivity, ranging from insulator to conductor.From the perspective of science and technology and economic development, semiconductors affect people's daily work and life. It was not until the 1930s that this material was recognized by the academic community.[2]
Discovery History
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The discovery of semiconductors actually goes back a long time.
In 1833, Faraday, the father of electronics, a British scientist, first discoveredSilver sulfideThe change of the resistance of silver sulfide with temperature is different from that of ordinary metals. Generally, the resistance of metals increases with temperature, but Faraday found that the resistance of silver sulfide materials decreases with temperature.This is the first discovery of semiconductor phenomenon.[3]
Soon, 1839FranceBecquerel discovered that semiconductor andelectrolyteThe junction formed by contact will generate a voltage under light, which is known laterPhotovoltaic effectThis is the second characteristic of the discovered semiconductor.[3]
In 1873, Smith in England found that the selenium crystal material was exposed to lightconductanceIncreasedPhotoconductive effectThis is the third characteristic of semiconductors.[3]
In 1874, Braun of Germany observed thatsulfideThe conductivity of is related to the direction of the applied electric field, that is, its conductivity isdirectional, add one at both endsForward voltage, it is conductive;If the voltage polarity is reversed, it will not conduct electricity, which is therectification effect , which is also the fourth characteristic unique to semiconductors.In the same year, Schuster discovered copper andCupric oxideRectification effect of.[3]
The period from 1879 to 1947 was the foundation periodPhysics revolution(relativityandquantum mechanics）It makes people knowMicrocosm(atoms and molecules), and then these new theories were successfully applied to new fields (including semiconductors)Energy band theoryIt has laid a solid theoretical foundation for semiconductor technology, and the progress of material growth technology has laid a material foundation for semiconductor technology (semiconductor materials require very pureMatrix material, very precise doping level).[11]
Although these four characteristics of semiconductor were discovered before 1880, the term semiconductor was first used by Koeniberg and Weiss in 1911.It was not until December 1947 that these four characteristics of semiconductors were summarizedBell LaboratoriesDone.[3]
In October 2019, an international scientific research team said that compared with only three parameters obtained in the traditional Hall measurement, the new technology in each testlight intensityUp to 7 parameters can be obtained under: includingelectrons and holes Ofmobility；Loader density, recombination lifetime, electron, hole and bipolar types under lightDiffusion length。[4]
（1）Element semiconductor。Element semiconductors refer to semiconductors composed of single elements, among which silicon and selenium were studied earlier.It is composed of the sameElement compositionThe solid materials with semiconductor characteristics of.At present, only silicon and germanium have good performance and are widely usedElectronic lightingAnd optoelectronic applications.Silicon is widely used in the semiconductor industry, which is mainly affected bysilicon dioxideCan be formed in device manufacturingMask, can improvesemiconductor device The stability of is conducive to automationindustrial production 。[2]
(2) InorganicCompositesemiconductor.Inorganic compounds mainly form semiconductor materials through a single element, of course, there are also semiconductor materials composed of multiple elements, and the main semiconductor properties include Group I, V6. Family VII;Family II and IV5. Family VI and VII;Family III and VVI family;Family IV and IVVI family;Family V and Family VI;The combination compounds of Group VI and Group VI are not all able to meet the requirements of semiconductor materials due to the influence of element characteristics and manufacturing methods.This half conductor is mainly used in high-speed devices,InP madetransistorOfSpeed ratioOther materialsDugao, mainly used in optoelectronic integrated circuits, antinuclear radiationDevice.aboutConductivityHigh material, mainly used in LED and other aspects.[2]
(3) Organic compound semiconductor.Organic compoundIt refers to the compound containing carbon bond in the molecule, which can be formed by vertical superposition of organic compound and carbon bondconduction bandThrough chemical addition, it can enterenergy band, this can happenconductivityTo form an organic compound semiconductor.Compared with previous semiconductors, this half conductor has low costSolubilityGood, light material and easy processing.The conductivity can be controlled by controlling the molecules. It has a wide range of applications, mainly used in organic films, organic lighting and other aspects.[2]
（5）Intrinsic semiconductor: free of impurities andLattice defectThe semiconductor of is called intrinsic semiconductor.At very low temperaturePrice bandyesFull belt, receivedThermal excitationSome electrons in the valence band will crossBandgapEnter higher energyEmpty belt, which becomesconduction band, the absence of an electron in the valence band forms a bandpositive electricityOfvacancy, calledhole。Hole conduction is not actual motion, but equivalent.Electronic conductionThe hole with equal charge will move in the opposite direction.[5]They are generated under the action of external electric fieldDirectional movementThe formation of macroscopic current is called electronic conduction andHole conduction。This is due toElectron hole pairThe mixed conductivity formed by the generation ofIntrinsic conductivity。The electrons in the conduction band will fall into the hole, and the electron hole pair will disappear, which is called recombination.The energy released during recombination becomeselectromagnetic radiation(luminescence) or the thermal vibration energy of the lattice (heating).At a certain temperature, the generation and recombination of electron hole pairs coexist and reachdynamic equilibriumAt this time, the semiconductor has certaincarrierDensity, thus having a certainresistivity。When the temperature increases, more electron hole pairs will be generated, the carrier density increases, and the resistivity decreases.Pure semiconductors without lattice defects have high resistivity and are rarely used in practice.[6]
semiconductor material Photovoltaic effect is the basic principle of solar cell operation.Photovoltaic applications of semiconductor materials have become a hot topic at this stage, which is currently the fastest growing and best developed in the worldclean energyMarket.The main manufacturing material of solar cells is semiconductor materials. The main criteria for judging the advantages and disadvantages of solar cells arePhotoelectric conversionThe higher the photoelectric conversion rate, the higher thework efficiencyThe higher.According to the different semiconductor materials used, solar cells are divided intoCrystalline silicon solar cell、Thin film batteryas well asIII-V compoundsBattery.[7]
Lighting applications
LED is a semiconductor light-emitting diode built on the semiconductor transistor. With LED technology, the semiconductor light source is small in size and can realize planar packagingCalorific valueLow cost, energy saving and high efficiency, long product lifereaction rate Quick, andGreen and environmental protectionIt is pollution-free and can also be developed into light, thin and small products. Once it comes out, it will be rapidly popularized and become a new generation of high-quality productsLighting source, has been widely used in our lives.Such as trafficindicator lightElectronic productsBacklight, urban nightscape beautification light sourceIndoor lightingAnd other fields.[7]
High power power conversion
alternating currentThe mutual conversion between DC and DC is very important for the use of electrical appliances, and it is a necessary protection for electrical appliances.This requires an equal power conversion device.silicon carbidebreakdown voltage High strength,Band gap widthWide, high thermal conductivity, so SiC semiconductor devices are very suitable for application inpower density andswitching frequency High occasion, power conversion device is one of them.The excellent performance of silicon carbide components in high temperature, high pressure and high frequency makes it widely used in deep well drilling and power generation devicesinverter, ElectricalHybrid vehicleOfEnergy converter，Light rail trainTraction power conversion and other fields.Due to the advantages of SiC itself and the current industry's emphasis on lightweight and highconversion efficiency Of semiconductor materials,SiC will replace Si and become the most widely used semiconductor material.[7]
Refrigeration technology
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Semiconductor refrigeration technologyIs currentRefrigeration technologyIt is widely used in.Crops inGreenhouseThe semiconductor refrigeration technology canambient temperatureEffective controlIn particular, some plants with high requirements for the environment can promote the growth of plants by using semiconductor refrigeration technology to shape the growth environment.Semiconductor refrigeration technology hasreversibility, can be used for refrigeration, can also be used for heating, the adjustment of ambient temperature has a good effect.[8]
Operating principle
Semiconductor refrigerationThe application principle of technology is based onPartier principleOn the basis of.In 1834, French scientist Partier discovered the refrigeration effect of semiconductor.peltier The principle is also called "Peltier effect", which is to make full use of two different conductors, use the circuit composed of A and B, and connectDC, which can be generated at the connector of the circuitJoule heatAt the same time, some other heat will be released. At this time, it will be found that the other joint is not releasing heat, but absorbing heat.This phenomenon is reversible. As long as the direction of the current is changed, the exothermic and endothermic operation can be adjusted. There is a relationship between the strength of the current and the absorbed heat and the released heatPositive proportional relationshipIt is also related to the nature of semiconductor itself.becauseMetallic materialsThe Peltier effect of is relatively weak, and the semiconductor materials based on the Peltier principle will also produce stronger effects. Therefore, semiconductor has become the main raw material in the refrigeration materials.However, in the use of this material, attention should be paid to theDimensionlessValues close to 1, higher than solidtheoretical modelIt is lower. The result obtained from the calculation of actual data is 4. Therefore, for the application of semiconductor materials, it is necessary to conduct in-depth research to make the semiconductor refrigeration technology reasonable.[8]
Application strategy
Semiconductor refrigeration technology has been widely used in the pharmaceutical field, industrial field, even in daily life, so this technology has a very important development prospect.
For example, conductor refrigeration technology is used in various modernRefrigeration equipmentMiddle, such as refrigerators, air conditioners, etc., can be equipped with electronicscooler。Semiconductor refrigeratorJust use itSemiconductor refrigeration technology。In specific applications, it can be used according to the needs of different customers to better meet customer requirements.
Different numbers of semiconductor refrigeration chips can be connected in parallel or in series according to the needs, and can be put in a proper position to play a role.In the 1950s, beforeSoviet UnionA small model refrigerator with a capacity of only 10 liters has been developed, which is very small and easy to use.Japan has developed a refrigerator specially used for storagered wineOf.The temperature should be strictly controlled, and the application of semiconductor refrigeration technology can meet the refrigeration requirements of refrigerators.With the continuous development of society, people are pursuingQuality of lifeAt the same time, the demand for refrigeration equipment is also getting higher and higher.When people use semiconductor refrigerators, they will find that the power consumption of such refrigerators is lower than that of traditional refrigerators, even up to 20%, with good energy-saving effect.[8]
The use of semiconductor air conditioners is different from the air conditioners used in daily life, but it is used in special places, such as engine rooms, submarines, etc.The relatively stable refrigeration technology can not only ensure rapid refrigeration, but also meet theSemiconductor refrigeration technologyRequirements.Some American companies found that another important function of semiconductor refrigeration technology is that it can ensure continuous power supply for more than 8 hours by reasonable application in active batteries.Semiconductor refrigeration technology has also been applied in automobile refrigeration equipment.Including agriculture, astronomy and medicine, semiconductor refrigeration technology also plays an important role.[8]
Difficulties and existing problems
（1） Difficulties in semiconductor refrigeration technology
The process of semiconductor refrigeration involves many parameters, and the conditions are complex and changeable.Any parameter will affect the cooling effect.Laboratory researchAs it is difficult to meet the specified noise, the laboratory environment needs to be studied, but someinfluence factorIt is difficult to discuss.Semiconductor refrigeration technologyIt is a refrigeration technology based on particle effect, which is reversible.Therefore, in the application process of refrigeration technology, there will be a large temperature difference between the hot and cold ends, which will inevitably affect the refrigeration effect.[8]
（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.Second, yesCold endCooling system andHot endCooling systemoptimal design However, the technology has not been upgraded. It is still in the theoretical stage and does not play a better role in the application, which leads to the semiconductor refrigeration technology can not be upgraded according to the application needs.Third, semiconductor refrigeration technology has limitations in other fields and related fields. Therefore, semiconductor refrigeration technology is rarely used. If the research on semiconductor refrigeration technology does not start from the perspective of application, it is difficult to expand in technology.Fourth,market economyIn the environment, with the development of science and technology, semiconductor refrigeration technology needs to be developed, and many aspects need to be considered.Attention should be paid to the application of semiconductor refrigeration technology, and various influencing factors should be considered to make this technology play a better role.[8]
new typesemiconductor material It is used more and more in industry.New semiconductor materialsStructural stability, with excellent electrical properties and low cost, it can be used to manufacture modernElectronic equipmentIt is widely used in China. Compared with other countries, there is still a big gap in this respect in China, which is usually manifested in the production and processing of some basic instruments. In recent years, many departments of the country have organized various groups in a unified way to effectively lead them in view of the weakness of China compared with other countries,Then work together to develop higher level semiconductor materials.Only in this way can we adapt to the progress and development of China's industrialization to a large extent and provide a stronger impetus for China's social progress.First, we need to furtherSuperlatticeResearch and development of quantum well materials. In terms of the current development background of semiconductor materials in China, we should greatly improve the ultrahigh brightness, red green blue light materials and optical communication materials. In the main research direction of future development, we should also update the generation ofelectronic deviceAnd circuit requirementsphotoelectronStructural materials, in the futureProduction processWe need to carefully analyze and discuss the needs of, and then meet the future direction of semiconductor development in the world. We need to select more optimized layout, and then do a good job in related development and research work. In this way, establishing a better communication mechanism between various research and development institutions and enterprises can to a large extent realize the development and utilization of high-temperature semiconductor materials and further.[10]
2023On March 30, the National Assembly of the Republic of Korea held a plenary meeting to pass the Tax Exception Control Law.According to the Act, semiconductors, etc. are legally listed as national strategic technologies of South Korea.[13]
