High-spec pain mask, the future of GaN-On-SiC

To talk about how popular GaN is, if you are a mobile phone manufacturer, you may be ridiculed as "outdated" if you don't launch a GaN fast charger. In the field of radio frequency, GaN is considered to be the future of high-power and high-performance application scenarios. What about GaN grown on SiC substrates? Can the strong combination of excellent genes create the king of the future?

The shackles of the “high-standard” market

GaN-On-SiC (gallium nitride on silicon carbide) combines the excellent thermal conductivity of SiC and the high power and high frequency characteristics of GaN. It has been widely used in power amplifiers (PA) in 5G base stations and RF front-ends in the defense field.

In the RF GaN industry, silicon carbide-based gallium nitride is indeed a well-deserved veteran. In addition to its deep penetration in military radars, it has also been the choice of 5G base station infrastructure for telecom OEMs such as Huawei, Nokia, and Samsung because it can better meet the high power, high frequency, and wide bandgap requirements of 5G technology.

Screenshot of Jiwei interview video

Industry insiders pointed out that base stations are still the main source of RF GaN revenue. "Currently, 5G base stations are still based on Sub-6GHz communication technology, but in the future they will be deployed in the direction of millimeter waves and will develop towards higher-frequency technologies," said Qiu Boshun, an analyst at market research firm Yole, in an interview with Jiwei Interview.

As the world accelerates 5G deployment, GaN on SiC is expected to replace Si-based LDMOS in the RF market in the near future. According to Yole, the GaN RF market will reach US$2.4 billion by 2026, with a compound annual growth rate of 18% from 2020 to 2026. Among them, the GaN on SiC RF market is expected to reach more than US$2.2 billion, with a compound annual growth rate of 17% during the forecast period.

Image source: Yole Development

Unlike the hot base station market, GaN-on-SiC is particularly quiet in the mobile terminal field and has not yet started large-scale application. It can be said that GaN-on-SiC, a veteran in the "high-end" market, is just a "rising star" waiting to rise in the mass market.

As the most important factor limiting GaN homoepitaxial growth, cost is also the primary problem that must be solved if silicon carbide-based gallium nitride is to increase its popularity among the general public.

Image source: Ping An Securities

In the past two years, the industry has begun to expand the substrate size of silicon carbide-based gallium nitride to seek better cost-effectiveness. Cree and Qorvo in the United States are upgrading to 6 inches. Last year, NXP announced that the first 6-inch GaN RF wafer factory built in Arizona, USA, was officially put into operation.

Qiu Boshun believes that NXP is a very critical example, representing that GaN on SiC is being adopted by mainstream manufacturers. The foreseeable growth of future demand is accelerating the evolution of production platforms from 4 inches to 6 inches. It is expected that by 2024, the number of 6-inch GaN on SiC in the overall market will exceed 4 inches, and 6 inches will gradually become mainstream.

NXP Arizona 6-inch GaN wafer fab opening ceremony

However, given the difficulty in manufacturing silicon carbide substrates, key technologies are still in the hands of a few American manufacturers such as Cree and II-VI. Therefore, Qiu Boshun believes that "the upgrade of process technology may still be dominated by American companies first", and there may be time differences in global promotion.

But in any case, for GaN-On-SiC to enter the "high-standard" market, it requires not only progress in the process, but also the coordinated development of the entire supply chain and comprehensive construction of the upstream and downstream industries.

The threat from silicon, the popular sweetheart

How long will it take for this day to arrive?

Before that, can silicon-based gallium nitride shine in the field of mobile terminals before silicon carbide-based gallium nitride? Compared with SiC, Si-based substrates are cheaper, easier to vertically integrate, and relatively easier to expand in size. However, for now, silicon-based gallium nitride PA is still in the exploratory stage in consumer electronics such as 5G mobile phones.

Yole pointed out in a previous report that the market capacity of silicon-based gallium nitride was small as of the second quarter of 2021, but silicon-based gallium nitride PA has attracted smartphone OEMs due to its large bandwidth and small size, and it is expected that it may soon be adopted by 5G mobile phone models supporting Sub-6GHz.

Nevertheless, in Qiu Boshun's view, GaN-on-Si PA still needs a "killer application" to open up the RF market. This process requires the first company to take the lead. Who will eventually stand up and complete the supply chain of GaN-on-Si PA?

So far, companies including Micron and STMicroelectronics are promoting silicon-based gallium nitride research and development plans. In the first half of the year, Raytheon and GlobalFoundries also announced that they would cooperate to develop new silicon-based gallium nitride semiconductors. Domestically, on June 5, Innoscience's Suzhou 8-inch silicon-based gallium nitride research and production base has officially entered the mass production stage.

Qiu Boshun told Jiwei.com that with the investment of these key companies, if silicon-based gallium nitride has the opportunity to be applied in products, some companies are also willing to adopt it, which may become an opportunity for silicon-based gallium nitride to enter the PA of 5G mobile phones.

Image source: Yole Development

But SweGaN, which has been researching GaN on SiC for more than a decade, does not think so.

Dr. Zhitai Chen, CTO and co-founder of Swedish semiconductor materials company SweGaN, said in an interview with eeNews that GaN on silicon is increasingly favored by IC designers, but the current technology still has many problems, the biggest of which is reliability.

It is understood that Si and GaN have great differences in lattice parameters and thermal expansion coefficients of 17% and 46% respectively, so that GaN single crystals grown on silicon often have defects such as cracks and low yields. Under the same conditions, the reliability and service life of SiC devices are better than Si.

According to Chen Zhitai, GaN must be grown to a thickness of 5μm on a silicon substrate to achieve good quality, but GaN-On-SiC only needs to grow to a thickness of 2μm. As the size of SiC substrates continues to expand, GaN epitaxial wafers with fewer defects and better quality will be grown.

In addition, SiC has high resistance characteristics, which is very beneficial to millimeter wave transmission and is necessary when designing high-frequency MMICs. In response to this, Qiu Boshun also pointed out that some companies can invest in new technologies in the future, especially through overall coordination from front-end processes to back-end processes to develop the potential of materials, which will be a new business opportunity for the entire supply chain.

Standing at the wind's edge

Whether it is 5G base stations or defense fields such as radars and satellites, or even the development of smartphones, China's speed has attracted worldwide attention. Behind a series of third-generation semiconductor industry policies, the domestic GaN-On-SiC industry is constantly influxing with new participants from substrates to epitaxy and then to the entire vertical process. "Overall, the current layout is relatively complete," said Qiu Boshun.

Market opportunities are coming. Are the "domestic third-generation and a half" products standing at the forefront ready?