Star materials in the RF field: GaAs and GaN
Semiconductor raw materials have gone through three stages of development: the first stage was the first-generation semiconductor raw materials represented by silicon (Si) and germanium (Ge); the second stage was represented by compounds such as gallium arsenide (GaAs) and indium phosphide (InP); the third stage was dominated by broadband semiconductor raw materials such as gallium nitride (GaN), silicon carbide (SiC), and zinc selenide (ZnSe).
The third generation semiconductor materials have a larger bandwidth, higher breakdown voltage, and good voltage and high temperature resistance, and are therefore more suitable for manufacturing high-frequency, high-temperature, and high-power RF components.
Compounds began to appear from the second generation of semiconductor raw materials, and these compounds have been widely used in the semiconductor field due to their excellent properties.
For example, GaAs has excellent physical performance advantages in the field of high-power transmission and is widely used in mobile phones, wireless local area networks, fiber optic communications, satellite communications, satellite positioning and other fields.
GaN has the advantages of low conduction loss and high current density, which can significantly reduce power loss and heat dissipation load. It can be applied to inverters, voltage regulators, transformers, wireless charging and other fields.
SiC is widely used in power conversion devices such as AC-DC converters due to its excellent performance under high temperature, high voltage, and high frequency conditions.
GaN, the rising star
GaN is the compound semiconductor with the greatest growth potential in the future. Compared with high-frequency processes such as GaAs and InP, GaN-made components have higher output power; compared with power processes such as LDMOS and SiC, GaN has better frequency characteristics.
Most Sub 6GHz cellular networks will use GaN components because LDMOS cannot withstand such high frequencies and GaAs is not ideal for high-power applications.
In addition, because higher frequencies reduce the coverage of each base station, more transistors need to be installed, which will drive the rapid expansion of the GaN market.
The output value of GaN components currently accounts for about 20% of the entire market, and Yole estimates that the proportion will increase to more than 50% by 2025.
(Data source: yole; Figure: Southwest Securities) Market share distribution of different materials
GaN HEMT has become a candidate technology for future large-scale base station power amplifiers. It is currently estimated that about 1.5 million base stations are newly built each year around the world. In the future, 5G networks will also be supplemented with micro base stations with smaller coverage areas and more dense distribution, which will stimulate the demand for GaN components.
Additionally, the defense market has been a major driver of GaN development over the past few decades and is currently being used in new generation air and ground radars.
(Data source: Qorvo ; Picture: Southwest Securities)
GaAs, the cornerstone of mobile phones
As one of the most mature compound semiconductors, GaAs is the cornerstone of power amplifiers (PA) in smartphone components.
According to StrategyAnalytics data, the total output value of the global GaAs component market (including IDM factory component output value) in 2018 was approximately US$8.87 billion, a record high, and the market concentration was high, with Qorvo's market share accounting for 26%.
Since GaAs has the high power and high linearity required for carrier aggregation and multiple-input multiple-output technology, GaAs will continue to be the mainstream technology in the frequency band below 6 GHz. In addition, GaAs also has certain applications in automotive electronics and military fields.
In summary, the above-mentioned III-V compound semiconductor components have excellent high-frequency characteristics and have long been regarded as the first choice for wireless applications in space technology.
With the explosive demand for broadband wireless communications and optical communications in the commercial sector, compound semiconductor process technology is being more widely used in high-frequency, high-power, low-noise wireless products and optoelectronic components. At the same time, it has also spread from handheld wireless communications to the technology development of 5G infrastructure and optical communications under the trend of the Internet of Things. As a senior RF expert, Qorvo has in-depth research in this field.
David Zhao, senior sales manager of Qorvo's mobile phone division, pointed out in a previous media interview that 5G has higher requirements for PA linearity, so the GaAs process with high voltage resistance is more popular. GaAs Die flip-chip technology has been widely adopted by QRVO. Compared with traditional GaAs wire bonding packaging, the flip-chip process makes the module thinner and more consistent. By coordinating SOI, CMOS and SAW/BAW flip-chip processes, SiP RF modules with smaller size and more functions become possible.
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