Metal terminator - gallium
What kind of element is gallium?
Gallium is in Group IIIA of the fourth period of the periodic table of elements. The melting point of pure gallium is very low, only 29.78°C, but its boiling point is as high as 2204.8°C. In summer, most of it exists in liquid form and can be melted in the palm of your hand. From the above properties, we can understand that the reason why gallium corrodes other metals is precisely because of its low melting point. When liquid gallium forms an alloy with other metals, we can see the magical phenomenon mentioned above. Its content in the earth's crust only accounts for about 0.001%. It was not until 140 years ago that humans discovered its existence. In 1871, when summarizing the periodic table of elements, the Russian chemist Mendeleev predicted that after zinc, aluminum would There is also an element below that has similar properties to the aluminum element, which is called an "aluminum-like element". In 1875, while studying the spectral line patterns of metal elements of the same family, the French scientist Bois-Baudran discovered a strange light band in sphalerite (ZnS), thus finding this "aluminum-like element" and then using his own Named after its motherland, France (Gaul, Latin Gallia), the symbol is Ga to represent the element. Therefore, in the history of chemical element discovery, gallium became the first element to be predicted and then confirmed in experiments.
"Navigator" in the electronic information age
Gallium itself is not a semiconductor, but a series of gallium-based compounds formed with arsenic, nitrogen, selenium, tellurium, phosphorus, antimony and other metals and non-metals are all high-quality semiconductor materials and are important materials for the development of microelectronic devices and optoelectronic devices. It can even be said that gallium leads the development direction of semiconductor materials and is the navigator of the electronic information era.
Gallium arsenide (GaAs) is a representative of the second generation of semiconductor materials. It is known as the "semiconductor aristocrat" because of its high price. It has the advantages of high frequency, high speed, high temperature resistance, good low temperature performance, low noise and strong radiation resistance. , so it occupies a major position in the field of microelectronic devices. Gallium arsenide has the ability to double as a semi-insulating material and a semiconductor material. Semi-insulating gallium arsenide materials are mainly used in radar, satellite television broadcasting, microwave and millimeter wave communications, wireless communications and optical fiber communications; semiconductor gallium arsenide materials are mainly used in optical communication active devices (LD), semiconductor light-emitting diodes ( LED), visible light lasers, near-infrared lasers, quantum well high-power lasers and high-efficiency solar cells and other optoelectronic fields. In addition, gallium arsenide plays an important role in the military field and is mainly used in radar, electronic warfare, satellite communications, etc., of which the proportion of radar applications is about 60%.
Gallium nitride (GaN) is an important third-generation semiconductor material with unique electromagnetic and optical properties such as high stability, high hardness, wide energy gap and high melting point. It is currently one of the most advanced semiconductor materials in the world. . The mobile phone fast charger mentioned at the beginning of this article is the application of gallium nitride in the field of fast charging. With the advantages of higher power, smaller size, and better heat dissipation, gallium nitride chargers can easily achieve high power in a small size and have gradually become the new favorite in the charger industry. Currently, the military and aerospace fields account for 40% of the total GaN device market, and the largest application market is still radar and electronic warfare systems. The high-brightness blue light-emitting diode developed based on GaN by Isamu Akasaki and Hiroshi Amano of Nagoya University in Japan and Shuji Nakamura of the University of California, Santa Barbara in the United States is an important breakthrough in the field of new energy-saving light sources and laid the foundation for the research of white light LEDs. The results also won the 2014 Nobel Prize in Physics.
Gallium oxide (Ga2O3) is a typical representative of the fourth generation of semiconductors and is even called the "new star in the semiconductor sky". As an emerging power semiconductor material, with its wider bandgap and excellent luminescence properties than the third-generation semiconductor materials silicon carbide (SiC) and gallium nitride (GaN), it has application advantages in the field of high-power and optoelectronic devices. increasingly obvious. In recent years, breakthrough progress in gallium oxide crystal growth technology has greatly promoted the research of related thin film epitaxy, high-brightness ultraviolet LED and other devices, and has become an international research hotspot in the field of ultra-wide bandgap semiconductors.