The Need for Advanced Wide Bandgap Power Electronics
PowerAmerica’s strategic roadmap for next generation wide bandgap (WBG) power electronics (PE) came out earlier this year. The public version of the roadmap includes a background/introduction and market forecast pertaining to silicon carbide (SiC) and gallium nitride (GaN) PE. I learned a great deal about SiC & GaN PE in this roadmap and I have copied the relevant sections below.
Our society has become increasingly dependent on complex devices, machines, and systems—from handheld electronic devices like smartphones and laptop computers to electric vehicles (EVs) and grid-scale renewable energy systems. None of these technologies would be possible without cross-functional semiconductor PE capable of converting power and controlling electrical energy (i.e., tuning voltage, current, and frequency) from the point of energy generation to distribution.
WBG semiconductors hold great promise to significantly outperform and eventually replace traditional Si-based PE technology. While there are research and development (R&D) efforts in various WBG semiconductors—including diamond, aluminum nitride, and gallium oxide—that could be used in advanced PE, SiC and GaN have currently reached a level of maturity that allows use in PE applications. SiC and GaN have enabled the development of compact (i.e., high power density), cost-effective, energy-efficient, and robust power components that operate at higher temperature, voltage, and frequency conditions.
Both SiC- and GaN-based power devices have distinct benefits for specific applications: SiC is generally a stronger candidate for PE above 1.2kV, while GaN is highly competitive for PE below 1.2kV. The device voltage range between 650V and 1.2kV is a competitive space that can be supported by either SiC or GaN technologies. Compared to Si, SiC-based power devices can operate at higher temperatures with higher thermal conductivity, higher breakdown voltage at lower on-stage resistance, faster switching speed, lower conduction and switching on-state loss, and exceptional radiation hardness. Advantages of GaN-based power devices include higher electron mobility and lower losses at higher frequencies, which can enable smaller devices with increased power density.
While WBG technologies offer significant capabilities that can advance PE, industry must overcome numerous challenges including high material and manufacturing costs, reliability perceptions, packaging and performance requirements, and difficulty coordinating efforts across the entire WBG PE ecosystem. Recent progress against these challenges in automotive applications, PV inverters, and power supplies is encouraging; however, SiC and GaN have not taken off as rapidly in traction applications, industrial motor drives, and wind turbines. Further strides are needed to begin manufacturing these devices at high volumes and competitive costs across the full range of useful applications.
Prices for SiC and GaN devices have been falling rapidly in the last few years, helping fuel recent market growth. SiC metal-oxide-semiconductor field-effect transistor (MOSFET) prices, for example, dropped 50% between 2012 and 2015 (according to IHS Markit). Though prices rose in 2017 due to wafer supply shortages, a growing number of wafer suppliers and improved wafer performance should allow prices to stabilize by 2019 and then continue falling for the foreseeable future. This increasing cost competitiveness has already helped SiC begin to dislodge Si in some applications (e.g., hybrid vehicles) and has enabled mass production of GaN-based end products (mainly in server and telecom rectifier power supplies). In addition, leading manufacturers now have trillions of hours of field device experience to assuage any reliability concerns that might dampen growth.
A recent study by IHS Markit projects annual SiC revenues will reach $10 billion by 2027, with hybrid and electric vehicles making up the vast majority of sales. Annual GaN revenues are projected to top $1.7 billion over the same timeframe, with power supplies, hybrid and electric vehicles, and military and aerospace applications holding the largest shares. In comparison, revenues for SiC and GaN combined were only $210 million2 in 2015. Across these applications, discrete power devices would account for most of the growth as they are expected to take off faster than power modules and integrated circuits.
A separate forecast from Cree Inc.3 also predicts EVs will present a tremendous growth opportunity for WBG materials, particularly SiC. To date, automakers have announced plans to spend $150 billion in the EV market.4 Cree estimates that even modest EV adoption—approximately 10% of total vehicles sales by 2027—could result in SiC revenues of $6 billion. The same forecast places the total SiC PE market at over $5 billion by 2022, largely driven by EV adoption but also industrial and telecom applications. For GaN, telecommunications stand out as an opportunity for strong growth. GaN devices support 10 times faster download speeds and better cellular coverage, which can enable the transition to 5G internet service.
The future is bright for WBG PE technologies. SiC and GaN have already proven their technical advantages over Si, and now decreasing prices are also driving adoption. SiC turned a corner in 2016 and GaN growth should shortly follow. For devices within certain voltage ranges, SiC and GaN will be viable options within the next 10 years and should continue to displace Si in the market.