Development and Application of Semiconductor Materials
According to the difference in their conductive properties, substances in the natural world can be divided into conductors with good conductivity (such as silver, copper, iron, etc.), insulators (such as rubber, ceramics, plastics, etc.) almost without conductivity, and semiconductors (such as germanium, silicon, GaAs).
Semiconductors are substances that have a conductive capability between a conductor and an insulator. Its electrical conductivity varies significantly with temperature, light, and dopant impurities. In particular, doping can change the conductivity capability and conductivity type of semiconductors, which is the basic principle widely used in the manufacture of various electronic components and integrated circuits.
The development and application of semiconductors will be specified in the following.
1. The Development of Semiconductor Materials
The first generation of semiconductors were "elemental semiconductors", typically silicon-based and germanium-based semiconductors. Among them, the silicon-based semiconductor technology is more mature and the application is more extensive. Generally the name of the elemental semiconductor is replaced by Silicon-based semiconductors.
The second generation of semiconductor materials is compound semiconductors. Compound semiconductors are represented by gallium arsenide (GaAs), indium phosphide (InP), and gallium nitride (GaN), and include many other III-V compound semiconductors. Among these compounds, most commonly used in commercial semiconductor devices are gallium arsenide (GaAs) and gallium arsenide (GaAsP), indium phosphide (InP), gallium arsenide (GaAlAs), and indium phosphide (InGaP). Among them, gallium arsenide technology is more mature and its application is more extensive.
2. The Application of Semiconductor Materials
The early application of semiconductor materials: The first application of semiconductors is to use its rectifying effect as a detector, which is a point contact diode (also known as a cat beard detector, that is, a metal probe on a semiconductor to detect electromagnetic waves). In addition to the detectors, in the early days, semiconductors were also used as rectifiers, photovoltaic cells, infrared detectors, etc. From 1907 to 1927, physicists in the United States developed crystal rectifiers, selenium rectifiers, and cuprous oxide rectifiers. In 1931, Lange and Bergman developed selenium photovoltaic cells. In 1932, Germany successfully developed semiconductor infrared detectors such as lead sulfide, lead selenide and lead telluride, which were used to detect aircraft and ships in World War II. In the Second World War, the Allied Forces in semiconductor research has also achieved great results. The United Kingdom used infrared detectors to detect German aircraft many times.
Today, semiconductors have been widely used in home appliances, communications, industrial manufacturing, aviation, aerospace and other fields. In 1994, the world market share of the electronics industry was 691 billion U.S. dollars, and in 1998 it increased to 935.8 billion U.S. dollars. Due to the recession of the U.S. economy, the decline in the semiconductor market has dropped from more than 150 billion U.S. dollars in 1995 to over 130 billion U.S. dollars in 1998. After several years of embarrassment, the semiconductor market has recovered.
3. The Development Direction of The Second Generation of Semiconductor Materials
The current development of the compound semiconductor industry is mainly reflected in the following five aspects.
1. Consumer optoelectronics. The ratio of optical storage, digital TV and global home electronics equipment to wireless control and data connectivity is increasing, and audio and video devices are becoming increasingly wireless. Coupled with the popularity of notebook computers, the market for such products has brought a huge new market for the application of compound semiconductor products.
2. Automotive optoelectronics market. At present, the automobile anti-collision radar has been applied to many high-end cars and will certainly become more and more popular in the future. Car anti-collision radar generally works in the millimeter wave band, so it is certainly inseparable from gallium arsenide or even indium phosphide, and its mid-frequency part will use silicon germanium. As the global auto industry is very large, it is a huge market that will surely be concurrent.
3. The rapid development of semiconductor lighting technology. The semiconductor light sources based on semiconductor light emitting diodes (LEDs), with great economic and technological value and market prospects, have many advantages such as small size, low calorific value, small power consumption, long life, fast reaction speed, environmental protection, impact-resistant and non-breakable, waste recyclable, and no pollution, and can be packaged flat and easily, In particular, LED-based semiconductor lighting products have the advantages of high-efficiency, energy-saving and green environmental protection. Under the dual background of limited global energy resources and sustainable environmental protection, they will trigger an epoch-making lighting revolution worldwide, becoming a new generation of electric light sources entering millions of households after incandescent lamp and fluorescent lamps. At present, LED has been widely used in large-screen display, traffic lights, mobile phone backlight, etc., began to be applied to urban nightscape beautification, landscape lights, floor lamp, flashlights, signs, etc.
4. A new generation of fiber optic communications technology. The new generation of 40Gbps optical communication equipment will soon be introduced to the market, replacing 25Gbps equipment and putting it into use. Many of these devices will use compound semiconductor integrated circuits such as indium phosphide, gallium arsenide, and silicon germanium.
5. Mobile communications technology is constantly moving in favor of compound semiconductor products. At present, the second-generation and half-generation (2.5G) technology has become the mainstream of mobile communication technology, and it is gradually transitioning to the third generation (3G). The second-generation and half-technology have higher requirements on the efficiency and heat dissipation of power amplifiers, which is beneficial to gallium arsenide devices. 3G technology requires higher operating frequencies, wider bandwidth and high linearity, which is also beneficial for gallium arsenide and silicon germanium technologies. The current concept of the fourth generation (4G) has been explicitly proposed. 4G technology has higher requirements for mobile phones. It requires the mobile phone to be able to access the wireless local area network (WLAN) in the building, and it can work to 2.4 GHz and 5.8 GHz, and it can work outdoors under any standard of second generation, half second generation and third generation. Therefore, this is a multi-functional, multi-band, multi-mode mobile terminal. From the system's compactness, of course, it would be desirable to implement single-chip integration (SOC), but a single silicon technology cannot achieve optimal performance in both versatility and mode. To integrate various functions to optimize performance, only system-in-package (SIP) can be used, that is, different processes such as silicon, silicon germanium, and gallium arsenide can be used to optimize different functions in the same package. This brings a new development prospects to the gallium arsenide (GaAs).
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