Electronics designers are now moving away from conventional Si-based power electronics and towards wide-bandgap solutions like gallium nitride (GaN) which not only deliver improved levels of device efficiency, speed and robustness but are a key enabler in the development of next generation power systems.
GaN enables higher efficiency, faster switching speeds, and greater power density than silicon and brings with it far-reaching implications for a number of different sectors such as industrial, automotive, and consumer, as well as computing, AI systems, solar inverters, chargers and adapters.
Since 2019 GaN devices have been embraced by the consumer sector and are expected to remain the main driver of growth in this market.
Infineon Technologies, STMicroelectronics, ROHM and Nexperia have become high-volume GaN transistor manufacturers but there is now a growing number of new entrants into the market.
Recently, Infineon unveiled the world’s first 300 mm power gallium nitride (GaN) wafer technology in an existing high-volume manufacturing environment – a significant step towards delivering commercial volumes of GaN-based power semiconductors.
According to the company’s CEO, Jochen Hanebeck, “This technological breakthrough will be an industry game-changer and enable us to unlock the full potential of gallium nitride.”
A significant advantage of 300 mm GaN technology is that it can utilise existing silicon manufacturing equipment as both use very similar processes, but it's that manufacturing process that remains the biggest challenge when it comes to GaN and its wider adoption, according to Rodney Pelzel, CTO of IQE, a leading supplier of advanced wafer products and material solutions.
According to Pelzel, “Getting GaN to work at scale remains difficult and consistent manufacturing is certainly the biggest challenge when it comes to its wider adoption.”
Pelzel has worked with epitaxy manufacturing for many years and been involved in the development of a broad range of different substrates.
“GaN was discovered back in the 1930s and it was found to have excellent RF, as well as optical properties. It is also very robust in harsh environmental conditions. The US government started to deploy GaN in radar systems back in the 1990s, while GaN-based LEDs were found to be much more efficient and could provide another possibility for blue and green LEDs.
“The substrate is the foundation upon which all microelectronic devices are built. It is the base material upon which epitaxial layers are deposited to form structures that are then, through microfabrication, turned into the end product,” Pelzel explained.
“IQE offers a broad range of compound semiconductor materials in single crystal substrate, ingot and polycrystalline forms and has contributed to the development of silicon, silicon carbide, sapphire and now GaN substrates. But GaN is a unique material, there is no native substrate from the beginning, so it can be difficult to make.”
Investment driving growth
The increasing investments in research and development activities focused on improving GaN semiconductor technology are certainly helping to fuel growth and IQE is not alone in developing innovative manufacturing techniques and advancing the quality and performance of GaN substrates.
GaN is a compound that’s made up of gallium and nitrogen and its Wurtzite crystal structure is both very strong and has a high melting point, which makes it suitable for semiconductor base materials in high-temperature settings.
Gallium nitride crystals can be grown on a variety of substrates, including sapphire, silicon carbide (SiC), and silicon (Si). The advantage of using silicon is that, as previously stated, you can also use the existing silicon manufacturing infrastructure – so there’s no need for specialised production sites.
“However, silicon and GaN are mismatched materials,” explained Pelzel, “and when you force GaN – a material with a certain structure and size - onto something with a different size that can cause strains within the material that can lead to problems.
“Silicon is very challenging to work with because there’s a bigger mismatch mechanically. Silicon likes to react to everything, so if you bring in gallium and nitrogen silicon nitrate, it can be hard to produce usable wafers without any defects.”
To date GaN has been used in a number of niche markets and the challenge has always been how do you move it into volume scale markets?
“Well, that’s already happened in the consumer market with the development of USB-C fast chargers, which are very efficient,” said Pelzel. “RF was never a big enough market on its own, but what we’ve seen with power electronics in recent years has completely changed the economics and dynamic of using GaN. The opportunities are huge.”
For example, Pelzel points to the boom in AI where surging demand has also resulted in energy usage rapidly increasing, so much so that and we simply can’t build enough power stations to keep up with the demand we’re seeing.
Speaking at electronica Gene Sheridan, CEO Navitas, highlighted that 95% of the world’s data centres were unable to support the power demands of servers running NVIDIA’s latest Blackwell GPUs, while unveiling the world’s first 8.5 kW power supply unit (PSU), powered by GaN and SiC technologies.
“Aside from the manufacturing issue with GaN there is also an issue with its consistency in terms of performance,” according to Pelzel. “With consumer devices the requirements are certainly less stringent, but should a GaN-based device fail in a data centre that is certainly more challenging – likewise with the automotive industry.”
Production issues
By growing a thin layer of aluminium gallium nitride (AlGaN) on top of a GaN crystal, it creates a strain at the interface that then induces a compensating two-dimensional electron gas (2DEG) which is then used to efficiently conduct electrons when an electric field is applied across it.
The 2DEG is highly conductive and increases the mobility of electrons from about 1000 cm2/V·s in unstrained GaN to between 1500 and 2000 cm2/V·s in the 2DEG region. That’s what makes it possible to then create transistors and integrated circuits that feature higher breakdown strength, faster switching speed, higher thermal conductivity and lower on-resistance than comparable silicon solutions.
But as Pelzel suggests, that 2DEG layer is highly sensitive to damage during manufacturing and can impact the overall transistor performance. So careful attention needs to be paid to the etching, passivation, and cleaning steps.
“Despite those challenges when it comes to manufacturing GaN devices the opportunities are too big to ignore,” said Pelzel.
“GaN technology can significantly improve the performance, efficiency, and reliability of automotive electronics, it can improve power conversion in data centres and GaN-based motor drives can operate at higher frequencies, enabling smoother and more precise control of robotic movements. And, as we’ve seen with consumer electronics, GaN can offer improved power conversion delivering higher efficiencies, smaller size, lighter weight, and faster charging than traditional silicon-based solutions.”
Pelzel concluded, “While gallium nitride and silicon are very similar in manufacturing processes the challenge is engineering rather than being a material science issue – but the GaN market is set to accelerate.
“The one big difference with GaN compared to silicon is that with silicon the innovation takes place after the wafer’s been created; with GaN the innovation is on the substrate. That will require us to better understand the risk points and re-order the supply chain going forward.
