I. Definition and production
Germanium sheet is a round sheet material made of pure germanium (Ge). In modern industry, its preparation process is relatively complicated. First, germanium dioxide is usually used as the raw material to obtain germanium by carbon reduction. Subsequently, the obtained germanium is further smelted and purified, and finally made into germanium sheets that meet specific requirements.
II. Characteristics
(I) Physical properties
1. Appearance and morphology: It is dark blue when it is in powder form, while the crystalline germanium sheet is a silvery white brittle metal. Its density is 5.35 g/cm³. Such a density allows the germanium sheet to have a relatively suitable volume while maintaining a certain mass, which is conducive to its application in various devices. The melting point is 937.4℃, and the boiling point is as high as 2830℃. This high melting and boiling point ensures that the germanium sheet can still maintain a stable solid structure in some high temperature environments and will not easily melt or vaporize.
2. Electrical properties: It has good semiconductor properties and high electron mobility, which means that electrons can move relatively quickly in germanium sheets, so that semiconductor devices based on germanium sheets can achieve faster signal transmission and processing speeds. At the same time, the hole mobility is also considerable, which is of great significance for the conduction and control of current in semiconductor devices. In addition, germanium sheets also have a certain resistivity, and can be controlled through specific processes to make their resistivity meet the needs of different application scenarios. For example, in some semiconductor devices, germanium sheets are required to have a lower resistivity to reduce resistance loss, while in other cases, the resistivity needs to be adjusted appropriately to achieve specific electrical functions.
3. Optical properties: High-purity germanium single crystals have a high refractive index and show good transparency to infrared rays, but do not transmit visible light and ultraviolet rays. This unique optical property makes germanium sheets play an irreplaceable role in the field of infrared optics. For example, in infrared optical systems, germanium sheets can be used as prisms or lenses that specifically transmit infrared light, refracting and focusing infrared light, thereby realizing the detection and imaging of infrared signals.
4. Thermal properties: The high thermal conductivity enables the germanium wafer to conduct heat more effectively during operation, dissipate the generated heat in time, and avoid device performance degradation or even damage due to heat accumulation. At the same time, the germanium wafer can work stably in the range of room temperature to higher temperatures. Its thermal stability ensures that devices based on germanium wafers can operate reliably under different ambient temperature conditions.
(II) Chemical properties
1. Stability: The chemical properties are stable. At room temperature, it will not react chemically with air or water vapor, which allows the germanium wafer to be stored for a long time in a general atmospheric environment without being oxidized or corroded. However, when the temperature rises to 600-700℃, the situation changes, and the germanium wafer will quickly react with oxygen in the air to form germanium dioxide.
2. Acidity and alkalinity: In common acids, hydrochloric acid and dilute sulfuric acid have no effect on germanium wafers. However, concentrated sulfuric acid can slowly dissolve germanium wafers when heated; in strong oxidizing acids such as nitric acid and aqua regia, germanium wafers are easily dissolved. For alkaline solution, the effect of ordinary alkaline solution on germanium sheet is very weak, but when the alkali is in a molten state and in the air, the germanium sheet can be quickly dissolved. In addition, germanium does not react with carbon. This feature prevents the germanium sheet from being contaminated by carbon when using a graphite crucible to melt germanium, ensuring the purity and performance of the germanium sheet.
III. Application fields
(I) Semiconductor field
1. Transistor manufacturing: High-purity germanium is a key material for manufacturing semiconductor devices. Germanium single crystals doped with trace amounts of specific impurities can be used to make various transistors. In the early development of electronic technology, germanium transistors played an important role. Although with the advancement of technology, silicon transistors have gradually dominated in many fields, germanium transistors still have unique advantages in some specific application scenarios, such as circuits with special requirements for low noise and high-frequency performance.
2. Rectifier production: Germanium sheets are also widely used in the production of rectifiers. The function of the rectifier is to convert alternating current into direct current. With its good semiconductor properties, germanium sheets can effectively realize the unidirectional conduction of current, thereby completing the rectification function. Compared with rectifiers made of other materials, rectifiers based on germanium sheets have better performance in some cases. For example, in some circuits with low voltage drop requirements, germanium rectifiers can achieve efficient rectification with less energy loss.
3. Other semiconductor devices: In addition to transistors and rectifiers, germanium sheets are also used to manufacture a variety of other semiconductor devices, such as some special diodes, some components in integrated circuits, etc. In these devices, the semiconductor properties of germanium sheets are fully utilized to achieve various functions such as signal amplification, conversion, and processing, providing strong support for the miniaturization and high performance of modern electronic devices.
(II) Optoelectronics field
1. Infrared optical system: Because germanium sheets have good transmittance and unique optical refractive properties for infrared rays, they have been widely used in infrared optical systems. For example, in infrared thermal imagers, lenses or windows made of germanium sheets can effectively collect and transmit infrared rays, focus the infrared radiation emitted by objects onto detectors, thereby realizing thermal imaging of objects, and are widely used in security monitoring, industrial detection, medical diagnosis, military reconnaissance and other fields. In industrial inspection, infrared thermal imaging technology can be used to detect the heating of equipment and discover potential faults in advance; in medical diagnosis, infrared thermal imaging can assist doctors in detecting the temperature distribution of the human body and help diagnose certain diseases.
2. Infrared detectors: Germanium wafers are one of the important materials for making infrared detectors. Infrared detectors can convert received infrared signals into electrical signals, thereby realizing the detection and measurement of infrared radiation. Infrared detectors based on germanium wafers have high sensitivity and response speed, and can quickly and accurately detect weak infrared signals. In the field of astronomy, it is used to detect infrared radiation emitted by celestial bodies to help astronomers study the physical properties and evolution of celestial bodies; in environmental monitoring, it can be used to monitor the concentration of infrared gases in the atmosphere and evaluate environmental pollution.
(III) Optical communication and optical measurement field
1. Photodiodes: In optical communication systems, photodiodes are key devices for realizing the mutual conversion between optical signals and electrical signals. Photodiodes made of germanium wafers have high photoelectric conversion efficiency and can quickly and accurately convert optical signals into electrical signals, or convert electrical signals into optical signals, thereby ensuring efficient transmission and processing of signals in optical communication systems. In optical fiber communication, photodiodes are used to receive optical signals transmitted in optical fibers and convert them into electrical signals for subsequent amplification, processing and transmission; in optical transmitter modules, they can convert electrical signals into optical signals and transmit them to achieve long-distance transmission of information.
2. Infrared detector arrays: In the field of optical measurement, infrared detector arrays are often used to accurately measure the intensity, distribution and other parameters of infrared radiation. Infrared detector arrays made of germanium sheets have good consistency and stability and can provide high-precision measurement results. For example, in spectral analysis instruments, infrared detector arrays can detect and analyze infrared light of different wavelengths to help researchers understand the composition and structure of substances; in the quality inspection process of industrial production, infrared detector arrays can be used to measure the surface temperature distribution of products and detect whether the products have defects.
(IV) Laser and solar cell fields
1. Laser: In some specific types of lasers, germanium sheets play a key role as an important component. The optical and electrical properties of germanium sheets can meet the specific requirements of lasers for materials. For example, in some infrared lasers, germanium sheets can be used to make lenses or other optical elements of laser resonators, and realize the generation and output of lasers through reflection, refraction and other operations of lasers. The high refractive index and good optical quality of germanium sheets help improve the performance of lasers, enabling them to output high-power, high-quality laser beams, and are widely used in material processing, medical cosmetology, scientific research experiments and other fields. In material processing, lasers can be used for high-precision processing operations such as cutting, welding, and punching; in medical cosmetology, lasers can be used for freckle removal, hair removal, skin rejuvenation and other treatments.
2. Solar cells: Although silicon-based solar cells dominate the market, germanium sheets also have unique advantages in some special solar cell applications. For example, in some solar cells for space applications, germanium sheets are often used as substrate materials. The thermal stability and electrical properties of germanium sheets can ensure that solar cells can still work stably under complex space environments, such as high temperature and radiation, and efficiently convert solar energy into electrical energy, providing reliable energy supply for satellites, space stations and other spacecraft. In addition, germanium sheets can also be combined with other materials to form a new type of solar cell structure, further improving the conversion efficiency and performance of solar cells.
IV. Production and quality control
(I) Production process
1. Raw material preparation: Germanium-containing ores or other germanium sources are usually selected as starting materials. Common germanium-containing ores include germanium stone, etc. Before processing these raw materials, they need to be finely beneficiated and pretreated to increase the germanium content and remove impurities. For example, through physical beneficiation methods such as gravity separation and flotation, the useful minerals in the germanium ore are separated from the gangue minerals; then chemical methods such as acid leaching and alkaline leaching are used to further extract and enrich the germanium element to obtain relatively pure germanium compounds such as germanium dioxide.
2. Extraction and refining of germanium: The obtained germanium dioxide is converted into metallic germanium by carbon reduction and other methods. During the reduction process, the reaction conditions, such as temperature, time, and the amount of reducing agent, need to be precisely controlled to ensure the full progress of the reduction reaction and the high purity output of germanium. The reduced germanium usually contains some impurities and needs to be further refined. Refining methods include zone melting, chemical purification, etc. Zone melting uses the difference in solubility between germanium and impurities at different temperatures, and through multiple melting and solidification processes, the impurities are gradually enriched in a specific area, thereby achieving the purification of germanium; chemical purification is to convert impurities into separable compounds through chemical reactions, and then remove impurities through filtration, extraction and other methods to obtain high-purity germanium.
3. Preparation of germanium sheets: The refined high-purity germanium is processed into germanium sheets. First, after melting the germanium, a specific crystal growth technique, such as the pulling method and the zone melting method, is used to grow a germanium single crystal. During the crystal growth process, parameters such as temperature, pressure, and crystal growth rate need to be strictly controlled to ensure that the grown germanium single crystal has a good crystal structure and electrical properties. Then, the germanium single crystal is cut into thin sheets of the required thickness using cutting equipment, and then through a series of processing processes such as grinding and polishing, the surface of the germanium sheet reaches the required smoothness and flatness requirements, and finally a germanium sheet that meets the quality standards is obtained.
(II) Quality Control
1. Purity detection: The purity of germanium wafers is one of the key factors affecting their performance. Advanced analytical detection technologies, such as inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS), are used to accurately determine the impurity content in germanium wafers. These detection technologies can detect trace impurity elements in germanium wafers, such as iron, copper, lead, etc., to ensure that the purity of germanium wafers meets the strict requirements of semiconductor, infrared optics and other application fields. For example, in the semiconductor field, the purity of germanium wafers is usually required to reach 99.999% or even higher purity levels to ensure the performance stability and reliability of semiconductor devices.
2. Crystal structure analysis: The crystal structure of germanium wafers is analyzed using technologies such as X-ray diffraction (XRD) to detect parameters such as crystal integrity and crystal orientation. A good crystal structure is the basis for germanium wafers to have excellent electrical and optical properties. Through XRD analysis, it can be determined whether there are defects in the crystal structure of the germanium wafer, such as dislocations and stacking faults, and whether the crystal orientation meets the design requirements. For some applications that have strict requirements on crystal orientation, such as making specific types of semiconductor devices or infrared optical elements, precise control of crystal orientation can significantly improve the performance of the device.
3. Surface quality detection: The surface quality of the germanium wafer also has an important impact on its performance in various applications. Use optical microscopes, scanning electron microscopes (SEM) and other equipment to observe the surface of the germanium wafer to detect whether there are scratches, particles, uneven defects on the surface. At the same time, the surface quality of the germanium wafer is evaluated by measuring parameters such as surface roughness and finish. In infrared optical applications, the finish of the germanium wafer directly affects its transmittance and reflectivity of infrared rays. If there are defects on the surface, it will cause infrared rays to scatter and absorb during propagation, reducing the performance of the optical system.
4. Electrical performance test: The electrical properties of the germanium wafer are fully tested, including the measurement of parameters such as resistivity, electron mobility, and hole mobility. Through standard test methods such as the four-probe method, the resistivity of the germanium wafer is accurately measured to understand its conductive properties; using equipment such as the Hall effect test system, the electron mobility and hole mobility are measured to evaluate the carrier transport capacity of the germanium wafer in semiconductor devices. The accurate measurement and control of these electrical performance parameters are crucial to ensure the performance consistency and reliability of semiconductor devices. In the production process, through real-time monitoring and adjustment of these parameters, problems in the production process can be discovered in time, and corresponding measures can be taken to improve them to ensure that the germanium wafers produced meet the needs of different application fields.
V. Safety and Storage
(I) Safety
1. Impact on human health: Germanium and its compounds can irritate the skin, mucous membranes and eyes to a certain extent. When the human body comes into contact with germanium wafers or their related compounds, if improper protection is not taken, it may cause symptoms such as skin allergies, redness and swelling; if it comes into contact with the eyes, it may cause discomfort such as eye stinging and tears. In the air, the maximum allowable concentration of Ge is 1mg/m³. Therefore, in the process of producing, processing and using germanium wafers, operators need to strictly take protective measures, such as wearing work clothes, masks and latex gloves and other labor protection supplies, to avoid direct contact with germanium wafers and their dust to prevent damage to the body.
2. Environmental impact: Although germanium itself has relatively high stability in the natural environment, some germanium-containing wastewater, waste gas and waste residue generated during the production process may cause certain pollution to the environment if they are directly discharged without proper treatment. For example, germanium-containing wastewater may pollute the soil and water bodies and affect the balance of the ecosystem. Therefore, relevant enterprises must strictly abide by environmental protection laws and regulations, and effectively treat and recycle the waste generated during the production process to reduce the negative impact on the environment.
(II) Storage
1. Storage environment: Germanium sheets should be stored in a cool, ventilated, dry, clean warehouse without chemical corrosion atmosphere. Keeping the storage environment cool and ventilated helps prevent the germanium sheets from oxidation or other chemical reactions due to high temperature or poor air circulation. A dry environment can prevent the germanium sheets from getting damp, because the germanium sheets may absorb moisture in a humid environment, thereby affecting their electrical properties and surface quality. At the same time, the warehouse should be kept clean to prevent dust and other impurities from adhering to the surface of the germanium sheets and adversely affecting their performance. In addition, ensure that there are no chemicals that can react chemically with germanium in the warehouse to prevent the germanium sheets from being corroded.
2. Storage method: Do not store or transport germanium wafers together with acid or alkali products. Acids and alkalis are highly corrosive and contact with germanium wafers may cause corrosion.
