What are the three generations of Semiconductor Materials?
The first generation of semiconductor material
The first generation of semiconductor materials mainly refers to silicon (Si) and germanium (Ge) materials. In the 1950s, Ge dominated the semiconductor market and was mainly used in low-voltage, low-frequency, medium-power transistors and photodetectors. However, Ge semiconductor devices were inferior in high temperature and radiation resistance, and were gradually replaced in the late 1960s by Silicon device. The semiconductor device made of Silicon material has high-temperature resistance and radiation resistance. The sputtered silicon dioxide (SiO2) film has high purity and good insulation performance, which greatly improves the stability and reliability of the device. Therefore, Silicon has become the most widely used semiconductor materials that more than 95% of semiconductor devices and more than 99% of integrated circuits are made of Silicon materials.
In the 21st century, its leading and core position in the semiconductor industry will remain unwavering. However, the physical properties of silicon materials limit their use in optoelectronic and high-frequency high power devices.
The second generation of semiconductor material
The second generation of semiconductor materials mainly refers to
1) compound semiconductor materials such as gallium arsenide (GaAs), indium antimonide (InSb);
2) ternary compound semiconductors such as GaAsAl, GaAsP; and
3) some solid solution semiconductors such as Ge-Si, GaAs- GaP;
4) glass semiconductor (also known as amorphous semiconductor), such as amorphous silicon, glass-state oxide semiconductor;
5) organic semiconductor, such as phthalocyanine, copper phthalocyanine, polyacrylonitrile, and etc.
They are mainly used in the production of high-speed, high-frequency, high-power and light-emitting electronic devices. They are excellent materials for making high-performance microwave, millimeter wave devices and light-emitting devices. Due to the rise of information technology and the Internet, they are also widely used in satellite communications, mobile communications, optical communications and GPS navigation.
However, GaAs and InP materials are scarce and therefore expensive. In addition, they are toxic and can pollute the environment. These shortcomings make the application of the second generation semiconductor materials have great limitations.
The third generation of semiconductor material
The third generation of semiconductor materials (that is, our focus today) are those materials with a wide bandgap (Eg≥2.3eV), represented by silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), diamond, and aluminum nitride (AlN). In terms of applications, the main applications of the third generation of semiconductor materials are semiconductor lighting, power electronics, lasers and detectors, and other fields, each with different industry maturity.
Compared with the first and second generation semiconductor materials, the third generation semiconductor materials have a wide band gap, high breakdown electric field, high thermal conductivity, high electron saturation rate and higher radiation resistance. Therefore, it is more suitable for making high temperature, high frequency, radiation resistant and high power devices.
Typical semiconductor materials
Silicon carbide single crystal
The technological maturity of silicon carbide is the highest in the field of wide bandgap semiconductor materials and is the core of wide bandgap semiconductors. Silicon carbide is a semiconductor compound with a wide band gap (Eg: 3.2 eV), a high breakdown electric field (4 x 106 V/cm), and a high thermal conductivity (4.9 W/cm.k).
The GaN material is an III-V compound semiconductor material synthesized by Johason et al. in 1928. GaN materials have good electrical properties, wide bandgap (3.39eV), high breakdown voltage (3×106V/cm), high electron mobility (room temperature 1000cm2/V·s), high heterojunction charge density (1× 1013cm-2), etc. Therefore, it is considered to be the most preferred material for studying short-wavelength optoelectronic devices and high-temperature high-frequency high-power devices.
GaN devices can operate at higher frequencies, higher power, and higher temperatures than silicon, gallium arsenide, germanium, and even silicon carbide devices. In addition, GaN devices can be used in the high-frequency range from 1 to 110 GHz, covering mobile communications, wireless networks, point-to-point and point-to-multipoint microwave communications, and radar applications.
In recent years, Group III nitrides represented by GaN have received extensive attention due to their application prospects in the field of optoelectronics and microwave devices. As a semiconductor material with unique optoelectronic properties, GaN applications can be divided into two parts: GaN semiconductor materials can replace some silicon and other compound semiconductor materials with excellent performance under high temperature and high frequency, high power operating conditions; develop new optoelectronic applications with the unique properties of GaN semiconductor materials with wide band gaps and blue light excitation.
AlN is a Group III nitride with a direct band gap of 0.7 to 3.4 eV and can be widely used in the field of optoelectronics. Compared with materials such as gallium arsenide, it covers a larger spectral bandwidth, so it is especially suitable for applications from deep ultraviolet to blue light. What’s more, Group III nitrides have good chemical stability, excellent thermal conductivity, high breakdown voltage, and low electrical constants, making it possible to operate at higher frequencies, higher power, higher temperatures and harsh environments. Therefore aluminum nitride is a promising semiconductor material.
ZnO is both a wide bandgap semiconductor and a multifunctional crystal with excellent photoelectric and piezoelectric properties. It is suitable for the fabrication of high-efficiency optoelectronic devices such as blue, ultraviolet light and detectors. It can also be used in the manufacture of gas sensing devices, surface acoustic wave devices, transparent high-power electronic devices, window materials for luminescent displays and solar cells, and varistor and piezoelectric conversion.
Although we have now developed into the third-generation semiconductor materials, the first and second generation semiconductor materials have not been eliminated and are still widely used. Why did the emergence of the second generation not replace the first generation? Can third generation semiconductors completely replace traditional semiconductor materials?
Silicon and compound semiconductors are two complementary materials. In the application of semiconductors, the two are often combined to take advantage of each other, so as to produce products that meet higher requirements, such as high-reliability, high-speed defense military products. Therefore, the first and second generation semiconductor materials are in a state of long-term common.
However, the third generation of wide bandgap semiconductor materials has many excellent properties, which can break through the development bottleneck of the first and second generation semiconductor materials. With the development of technology, the third generation is expected to completely replace the first and second generation semiconductor materials.
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