Gallium nitride is starting to make broader inroads in the lower-end of the high-voltage, wide-bandgap power FET market, where silicon carbide has been the technology of choice. This shift is driven by lower costs and processes that are more compatible with bulk silicon.

Efficiency, power density (size), and cost are the three major concerns in power electronics, and GaN can meet all three criteria. However, to satisfy all of those criteria consistently, the semiconductor ecosystem needs to develop best practices for test, inspection, and metrology, determining what works best for which applications and under varying conditions.

Power ICs play an essential role in stepping up and down voltage levels from one power source to another. GaN is used extensively today in smart phone and laptop adapters, but market opportunities are beginning to widen for this technology. GaN likely will play a significant role in both data centers and automotive applications [1]. Data centers are expanding rapidly due to the focus on AI and a build-out at the edge. And automotive is keen to use GaN power ICs for inverter modules because they will be cheaper than SiC, as well as for onboard battery chargers (OBCs) and various DC-DC conversions from the battery to different applications in the vehicle.

Fig. 1: Current and future fields of interest for GaN and SiC power devices. Source A. Meixner/Semiconductor Engineering

But to enter new markets, GaN device manufactures need to more quickly ramp up new processes and their associated products. Because GaN for power transistors is a developing process technology, measurement data is critical to qualify both the manufacturing process and the reliability of the new semiconductor technology and resulting product.

Much of GaN’s success will depend on metrology and inspection solutions that offer high throughput, as well as non-destructive testing methods such as optical and X-ray. Electron microscopy is useful for drilling down into key device parameters and defect mechanisms. And electrical tests provide complementary data that assists with product/process validation, reliability and qualification, system-level validation, as well as being used for production screening.

Silicon carbide (SiC) remains the material of choice for very high-voltage applications. It offers better performance and higher efficiency than silicon. But SiC is expensive. It requires different equipment than silicon, it’s difficult to grow SiC ingots, and today there is limited wafer capacity.

In contrast, GaN offers some of the same desirable characteristics as SiC and can operate at even higher switching speeds. GaN wafer production is cheaper because it can be created on a silicon substrate utilizing typical silicon processing equipment other than the GaN epitaxial deposition tool. That enables a fab/foundry with a silicon CMOS process to ramp a GaN process with an engineering team experienced in GaN.

The cost comparison isn’t entirely apples-to-apples, of course. The highest-voltage GaN on the market today uses silicon on sapphire (SoS) or other engineered substrates, which are more expensive. But below those voltages, GaN typically has a cost advantage, and that has sparked renewed interest in this technology.

“GaN-based products increase the performance envelopes relative to the incumbent and mature silicon-based technologies,” said Vineet Pancholi, senior director of test technology at Amkor. “Switching speeds with GaN enable the application in ways never possible with silicon. But as the GaN production volumes ramp, these products have extreme economic pressures. The production test list includes static attributes. However, the transient and dynamic attributes are the primary benefit of GaN in the end application.”

Others agree. “The world needs cheaper material, and GaN is easy to build,” said Frank Heidemann, vice president and technology leader of SET at NI/Emerson Test & Measurement. “Gallium nitride has a huge success in the lower voltages ranges — anything up to 500V. This is where the GaN process is very well under control. The problem now is building in higher voltages is a challenge. In the near future there will be products at even higher voltage levels.”

Those higher-voltage applications require new process recipes, new power IC designs, and subsequently product/process validation and qualification.

GaN HEMT properties
Improving the processes needed to create GaN high-electron-mobility transistors (HEMTs) requires a deep understanding of the material properties and the manufacturing consequences of layering these materials.

The underlying physics and structure of wide-bandgap devices significantly differs from silicon high-voltage transistors. Silicon transistors rely on doping of p and n materials. When voltage is applied at the gate, it creates a channel for current to flow from source to drain. In contrast, wide-bandgap transistors are built by layering thin films of different materials, which differ in their bandgap energy. [2] Applying a voltage to the gate enables an electron exchange between the two materials, driving those electrons along the channel between source and drain.

Fig. 2. Cross-sectional animation of e-mode GaN HEMT device. Source: Zeiss Microscopy

“GaN devices rely on two-dimensional electron gas (2DEG) created at the GaN and AlGaN interface to conduct current at high speed,” said Jiangtao Hu, senior director of product marketing at Onto Innovation. “To enable high electron mobility, the epitaxy process creating complex multi-layer crystalline films must be carefully monitored and controlled, ensuring critical film properties such as thickness, composition, and interface roughness are within a tight spec. The ongoing trend of expanding wafer sizes further requires the measurement to be on-product and non-destructive for uniformity control.”

Fig. 3: SEM cross-section of enhancement-mode GaN HEMT built on silicon which requires a superlattice. Source: Zeiss Microscopy

Furthermore, each layer’s electrical properties need to be understood. “It is of utmost importance to determine, as early as possible in the manufacturing process, the electrical characteristics of the structures, the sheet resistance of the 2DEG, the carrier concentration, and the mobility of carriers in the channel, preferably at the wafer level in a non-destructive assessment,” said Christophe Maleville, CTO and senior executive vice president of innovation at Soitec.

Developing process recipes for GaN HEMT devices at higher operating ranges require measurements taken during wafer manufacturing and device testing, both for qualification of a process/product and production manufacturing. Inspection, metrology, and electrical tests focus on process anomalies and defects, which impact the device performance.

“Crystal defects such as dislocations and stacking faults, which can form during deposition and subsequently be grown over and buried, can create long-term reliability concerns even if the devices pass initial testing,” said David Taraci, business development manager of electronics strategic accounts at ZEISS Research Microscopy Solutions. “Gate oxides can pinch off during deposition, creating voids which may not manifest as an issue immediately.”

The quality of the buffer layer is critical because it affects the breakdown voltage. “The maximum breakdown voltage of the devices will be ultimately limited by the breakdown of the buffer layer grown in between the Si substrate and the GaN channel,” said Soitec’s Maleville. “An electrical assessment (IV at high voltage) requires destructive measurements as well as device isolation. This is performed on a sample basis only.”

One way to raise the voltage limit of a GaN device is to add a ‘gate driver’ which keeps it reliable at higher voltages. But to further expand GaN technology’s performance envelope to higher voltage operation engineers need to comprehend a new GaN device reliability properties.

“We are supporting GaN lifetime validation, which is the prediction of a mission characteristic of lifetime for gallium nitride power devices,” said Emerson’s Heidemann. “Engineers build physics-based failure models of these devices. Next, they investigate the acceleration factors. How can we really make tests and verification properly so that we can assess lifetime health?”

The qualification procedures necessitate life-stressing testing, which duplicates predicated mission profile usage, as well as electrical testing, after each life-stress period. That allows engineers to determine shifts in transistor characteristics and outright failures. For example, life stress periods could start with 4,000 hours and increase in 1,000-hour increments to 12,000 hours, during which time the device is turned on/off with specific durations of ‘on’ times.

“Reliability predictions are based upon application mission profiles,” said Stephanie Watts Butler, independent consultant and vice president of industry and standards in the IEEE Power Electronics Society. “In some cases, GaN is going into a new application, or being used differently than silicon, and the mission profile needs to be elucidated. This is one area that the industry is focused upon together.”

As an example of this effort, Butler pointed to JEDEC JEP186 spec [3], which provides guidelines for specifying the breakdown voltage for GaN HEMT devices. “JEDEC and IEC both are issuing guideline documents for methods for test and characterization of wide-bandgap devices, as well as reliability and qualification procedures, and datasheet parameters to enable wide bandgap devices, including GaN, to ramp faster with higher quality in the marketplace,” she said.

Electrical tests remain essential to screening for both time-zero and reliability-associated defects (e.g. infant mortality and reduced lifetime). This holds true for screening wafers, singulated die, and packaged devices. And test content includes tests specific to GaN HEMT power devices performance specifications and tests more directed at defect detection.

Due to inherent device differences, the GaN test list varies in some significant ways from Si and SiC power ICs. Assessing GaN health for qualification and manufacturing purposes requires both static and dynamic tests (SiC DC and AC). A partial list includes zero gate voltage drain leakage current, rise time, fall time, dynamic RDS_on, and dielectric integrity tests.

“These are very time-intensive measurement techniques for GaN devices,” said Tom Tran, product manager for power discrete test products at Teradyne. “On top of the static measurement techniques is the concern about trapped charge — both for functionality and efficiency — revealed through dynamic RDS_on testing.”

Transient tests are necessary for qualification and production purposes due to the high electron mobility, which is what gives GaN HEMT its high switching speed. “From a test standpoint, static test failures indicate basic processing failures, while transient switching failures indicate marginal or process excursions,” said Amkor’s Vineet Pancholi. “Both tests continue to be important to our customers until process maturity is achieved. With the extended range of voltage, current, and switching operations, mainstream test equipment suppliers have been adding complementary instrumentation capabilities.”

And ATE suppliers look to reduce test time, which reduces cost. “Both static and dynamic test requirements drive very high test times,” said Teradyne’s Tran. “But the GaN of today is very different than GaN from a decade ago. We’re able to accelerate this testing just due to the core nature of our ATE architecture. We think there is the possibility further reducing the cost of test for our customers.”

Tools for process control and quality management
GaN HEMT devices’ reliance on thin-film processes highlights the need to understand the material properties and the nature of the interfaces between each layer. That requires tools for process control, yield management, and failure analysis.

“GaN device performance is highly reflective of the film characteristics used in its manufacture,” said Mike McIntyre, director of software product management at Onto Innovation. “The smallest process variations when it comes to film thickness, film stress, line width or even crystalline make-up, can have a dramatic impact on how the device performs, or even if it is usable in its target market. This lack of tolerance to any variation places a greater burden on engineers to understand the factors that correlate to device performance and its profitability.”

Inspection methods that are non-destructive vary in throughput time and in the level of detail provided for engineers to make decisions. While optical methods are fast and provide full wafer coverage, they cannot accurately classify chemical or structural defects for engineers/technicians to review. In contrast, destructive methods provide the information that’s needed to truly understand the nature of the defects. For example, conductive atomic force microscopy (AFM) probing remains slow, but it can identify electrical nature of a defect. And to truly comprehend crystallographic defects and the chemical nature of impurities, engineers can turn to electron microscopy based methods.

One way to assess thin films is with X-rays. “High resolution X-ray measurements are useful to provide production control of the wafer crystalline quality and defects in the buffer, said Soitec’s Maleville. “Minor changes in composition of the buffer, barrier, or capping layer, as well as their layer thickness, can result in significant deviations in device performance. Thickness of the layers, in particular the top cap, barrier, and spacer layers, are typically measured by XRD. However, the throughput of XRD systems is low. Alternatively, ellipsometry offers a reasonably good throughput measurement with more data points for both development and production mode scenarios.”

Optical techniques have been the standard for thin film assessment in the semiconductor industry. Inspection equipment providers have long been on the continuation improvement always evolving journey to improve accuracy, precision and throughput. Providing better metrology tools helps device makers with process control and yield management.

“Recently, we successfully developed a non-destructive on product measurement capability for GaN epi process monitoring,” said Onto’s Hu. “It takes advantage of our advanced optical film experience and our modeling software to simultaneously measure multi-layer epi film thickness, composition, and interface roughness on product wafers.”

Fig. 4: Metrology measurements on GaN for roughness and for Al concentration. Source: Onto Innovation

Assessing the electrical characteristics — 2DEG sheet resistance, channel carrier mobility, and concentration are required for controlling the manufacturing process. A non-destructive assessment would be an improvement over currently used destructive techniques (e.g. SEM). The solutions used for other power ICs do not work for GaN HEMT. As of today, no one has come up with a commercial solution.

Inspection looks for yield impacting defects, as well as defects that affect wafer acceptance in the case of companies that provide engineered substrates.

“Defect inspection for incoming silicon wafers looks for particles, scratches, and other anomalies that might seed imperfections in the subsequent buffer and crystal growth,” said Antonio Mani, business development manager at Thermo Fisher Scientific. “After the growth of the buffer and termination layers, followed by the growth of the doped GaN layers, another set of inspections is carried out. In this case, it is more focused on the detection of cracks, other macroscopic defects (micropipes, carrots), and looking for micro-pits, which are associated to threading dislocations that have survived the buffer layer and are surfacing at the top GaN surface.”

Mani noted that follow-up inspection methods for Si and GaN devices are similar. The difference is the importance in connecting observations back to post-epi results.

More accurate defect libraries would shorten inspection time. “The lack of standardization of surface defect analysis impedes progress,” said Soitec’s Maleville. “Different tools are available on the market, while defect libraries are still being developed essentially by the different user. This lack of globally accepted method and standard defect library for surface defect analysis is slowing down the GaN surface qualification process.”

Whether it involves a manufacturing test failure or a field return, the necessary steps for determining root cause on a problematic packaged part begins with fault isolation. “Given the direct nature of the bandgap of GaN and its operating window in terms of voltage/frequency/power density, classical methods of fault isolation (e.g. optical emission spectroscopy) are forced to focus on different wavelengths and different ranges of excitation of the typical electrical defects,” said Thermo Fisher’s Mani. “Hot carrier pairs are just one example, which highlights the radical difference between GaN and silicon devices.”

In addition to fault isolation there are challenges in creating a device cross-section with focused-ion beam milling methods.

“Several challenges exist in FA for GaN power ICs,” said Zeiss’ Taraci. “In any completed device, in particular, there are numerous materials and layers present for stress mitigation/relaxation and thermal management, depending on whether we are talking enhancement- or depletion-mode devices. Length-scale can be difficult to manage as you are working with these samples, because they have structures of varying dimension present in close proximity. Many of the structures are quite unique to power GaN and can pose challenges themselves in cross-section and analyses. Beam-milling approaches have to be tailored to prevent heavy re-deposition and masking, and are dependent on material, lattice orientation, current, geometry, etc.”

Conclusion
To be successful in bringing new GaN power ICs to new application space engineers and their equipment suppliers need faster process development and a reduction in overall costs. For HEMT devices, it’s understanding the resulting layers and their material properties. This requires a host of metrology, inspection, test, and failure analysis steps to comprehend the issues, and to provide feedback data from experiments and qualifications for process and design improvements.

References

[1] M. Buffolo et al., “Review and Outlook on GaN and SiC Power Devices: Industrial State-of-the-Art, Applications, and Perspectives,” in IEEE Transactions on Electron Devices, March 2024, open access, https://ieeexplore.ieee.org/document/10388225

[2] High electron mobility transistor (HEMT) https://en.wikipedia.org/wiki/High-electron-mobility_transistor

[3] Guideline to specify a transient off-state withstand voltage robustness indicated in datasheets for lateral GaN power conversion devices, JEP186, version 1.0, December 2021. https://www.jedec.org/standards-documents/docs/jep186

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Attention nowadays has turned to the energy consumption of systems that run on electricity. At the moment, the discussion is focused on electricity consumption in data centers: if this continues to rise at its current rate, it will account for a significant proportion of global electricity consumption in the future. Yet there are other, less visible electricity consumers whose power needs are also constantly growing. One example is mobile communications, where ongoing expansion – especially with the new current 5G standard and the future 6G standard – is pushing up the number of base stations required. This, too, will drive up electricity demand, as the latter increases linearly with the number of stations; at least, if the demand per base station is not reduced. Another example is electronics for the management of household appliances and in the industrial sector: more and more such systems are being installed, and their electronics are becoming significantly more powerful. They are not currently optimized for power consumption, but rather for performance.

This state of affairs simply cannot continue into the future for two reasons: first, the price of electricity will continue to rise worldwide; and second, many companies are committed to becoming carbon neutral. Their desire for carbon neutrality in turn makes electricity yet more expensive and restricts the overall quantity much more severely. As a result, there will be a significant demand for efficient electronics in the coming years, particularly as regards electricity consumption.

This development is already evident today, especially in power electronics, where the use of new semiconductor materials such as GaN or SiC has made it possible to reduce power consumption. A key driver for the development and introduction of such new materials was the electric car market, as reduced losses in the electronics leads directly to increased vehicle range. In the future, these materials will also find their way into other areas; for instance, they are already beginning to establish themselves in voltage transformers in various industries. However, this shift requires more factories and more suppliers for production, and further work also needs to be carried out to develop appropriate circuit concepts for these technologies.

In addition to the use of new materials, other concepts to reduce energy consumption are needed. The data center sector will require increasingly better-adapted circuits – ones that have been developed for a specific task, and as a result can perform this task much more efficiently than universal processors. This involves striking the optimum balance between universal architectures, such as microprocessors and graphics cards, and highly specialized architectures that are suitable for only one use case. Some products will also fall between these two extremes. The increased energy efficiency is then “purchased” through the effort and expense of developing exceptionally specially adapted architectures. It’s important to note that the more specialized an adapted architecture is, the smaller the market for it. That means the only way such architectures will be economically viable is if they can be developed efficiently. This calls for new approaches to derive these architectures directly from high-level hardware/software optimization, without the additional implementation steps that are still necessary today. In sum, the only way to make this approach possible is by using novel concepts and tools to generate circuits directly from a high-level description.

The post Efficient Electronics appeared first on Semiconductor Engineering.

Field-programmable gate arrays (FPGAs) are a critical component of both digital and hybrid phased array technology. Powering FPGAs for aerospace and defense applications comes with its own set of challenges, especially because these applications require higher reliability than many industrial or consumer technologies.

This blog post will provide a brief history on beamforming and beam-steering technologies for defense applications, a guide on powering defense and space FPGAs, and a reflection on the future of A&D communications systems.

Background

Active electronically scanned array (AESA) and phased array systems are more affordable and available than ever, namely in full digital and hybrid configuration. These systems can cover a wide RF/uW frequency spectrum and are suitable for use in RADAR and other military communications systems. AESA and phased array systems also boast advanced capabilities in beamforming and beam-steering technologies.

The emergence of 5G communications and commercial space data communications, coupled with advancements in semiconductor efficiency, has enabled companies to deploy innovative phased-array designs. However, roadblocks in efficiently powering these systems given watts consumed and dissipated, plus size and geometry constraints, can complicate development for designers.

Recent developments

Despite digital phased array technologies providing improved performance across a large part of the RF/uW frequency spectrum, their deployment is hindered by various factors. Cost barriers, power consumption, thermal constraints, latency concerns, and efficiency losses in the amplification and gain stages are some key hurdles.

Hybrid phased array is an ideal solution for meeting system level requirements without compromising on cost or power losses. This technology allows for less power consumption and reduced thermal concerns, paving the way for cost-saving solutions. The “digitizers” of hybrid phased array, such as FPGAs, are fewer and farther away from the antenna.

Powering FPGAs

FPGAs are valuable in their ability to perform extremely fast calculations in support of signal isolations, Fast Fourier Transformers (FFTs), I/Q data extractions, and in functions that form and steer radio-frequency beams. However, a key challenge in working with FPGAs lies in the necessity for consistent, sequenced power delivery.

Conclusion and future considerations

Complexities and challenges associated with deploying digital assets should not overlook industry advancements in powering FPGAs within phased array systems. With a focused approach, thermal management challenges can be mitigated, and performance optimized. Existing power solutions provide a strong and mature foundation for the on-going development and deployment of next-generation phased array systems within military and space applications. For a full guide on FPGA power considerations in aerospace and defense applications, take a look at our feature in Military Embedded Systems magazine.

The post Optimize Power For RF/μW Hybrid And Digital Phased Arrays appeared first on Semiconductor Engineering.

Field-programmable gate arrays (FPGAs) are a critical component of both digital and hybrid phased array technology. Powering FPGAs for aerospace and defense applications comes with its own set of challenges, especially because these applications require higher reliability than many industrial or consumer technologies.

This blog post will provide a brief history on beamforming and beam-steering technologies for defense applications, a guide on powering defense and space FPGAs, and a reflection on the future of A&D communications systems.

Background

Active electronically scanned array (AESA) and phased array systems are more affordable and available than ever, namely in full digital and hybrid configuration. These systems can cover a wide RF/uW frequency spectrum and are suitable for use in RADAR and other military communications systems. AESA and phased array systems also boast advanced capabilities in beamforming and beam-steering technologies.

The emergence of 5G communications and commercial space data communications, coupled with advancements in semiconductor efficiency, has enabled companies to deploy innovative phased-array designs. However, roadblocks in efficiently powering these systems given watts consumed and dissipated, plus size and geometry constraints, can complicate development for designers.

Recent developments

Despite digital phased array technologies providing improved performance across a large part of the RF/uW frequency spectrum, their deployment is hindered by various factors. Cost barriers, power consumption, thermal constraints, latency concerns, and efficiency losses in the amplification and gain stages are some key hurdles.

Hybrid phased array is an ideal solution for meeting system level requirements without compromising on cost or power losses. This technology allows for less power consumption and reduced thermal concerns, paving the way for cost-saving solutions. The “digitizers” of hybrid phased array, such as FPGAs, are fewer and farther away from the antenna.

Powering FPGAs

FPGAs are valuable in their ability to perform extremely fast calculations in support of signal isolations, Fast Fourier Transformers (FFTs), I/Q data extractions, and in functions that form and steer radio-frequency beams. However, a key challenge in working with FPGAs lies in the necessity for consistent, sequenced power delivery.

Conclusion and future considerations

Complexities and challenges associated with deploying digital assets should not overlook industry advancements in powering FPGAs within phased array systems. With a focused approach, thermal management challenges can be mitigated, and performance optimized. Existing power solutions provide a strong and mature foundation for the on-going development and deployment of next-generation phased array systems within military and space applications. For a full guide on FPGA power considerations in aerospace and defense applications, take a look at our feature in Military Embedded Systems magazine.

The post Optimize Power For RF/μW Hybrid And Digital Phased Arrays appeared first on Semiconductor Engineering.

The need to mitigate climate change is driving a need to electrify our infrastructure, vehicles, and appliances, which can then be charged and powered by renewable energy sources. The most visible and impactful electrification is now under way for electric vehicles (EVs). Beyond the transition to electric engines, several new features and technologies are driving the electrification of vehicles. The number of sensors in a vehicle is skyrocketing, driven by autonomous driving and other safety features, while a modern software-defined vehicle (SDV) is electrifying everything from air-conditioned seats to self-parking technology.

An important technology for EVs and SDVs is power modules. These are super high-voltage devices that convert one form of electricity to another (e.g., AC to DC), which is necessary to convert the vehicle battery energy to a current that can run the vehicles electrical system, including the drive train. These modules demand the highest power loads and are rated at 1000s of voltages – and the design of power devices, which are the fundamental electronic component of the power modules, is crucial, as a bad design can lead to catastrophe events.

Power devices, much more than other types of electrical devices, are designed for specific applications. In comparison, logic transistors can be used in everything from toasters to smartphones. Not only does the architecture of power devices change at higher voltages, different power ratings, or higher switching frequencies as needed, but the material can change as well.

New power requirements need wide-band gap materials

To meet new and future power demands for EVs, electric infrastructure, and other novel electrical systems, wide-band gap (WBG) materials are being developed and introduced. Silicon carbide (SiC) IGBTs are now available and being deployed, while gallium arsenide (GaN) HEMTs are a promising technology that is in the development stage.

Power density vs. switching frequency of power devices based on different materials.

Continuing with our EV example, SiC inverters can generally increase the potential range by approximately 10%, even after accounting for other design considerations. In addition, increasing the drive train voltage from 400V range to 800V can reduce the charging speeds by half. These voltages are only possible to realize with wide-band gap materials like SiC-based power devices. Tesla introduced SiC MOSFETs into its Model S back in 2018. Since then, numerous automotive manufacturers have also adopted SiC in their EVs, including Hyundai and BMW, for example.

GaN still has many design hurdles to overcame to improve reliability and decrease cost – but if it can be made affordable, perhaps the next realization of EVs will allow for charging in seconds with ranges of thousands of miles.

Simulating power devices

Because of the huge number of design parameters, simulation is important in the design of power devices. One crucial part for device design is the calculation of the breakdown voltage – the voltage at which the device can essentially melt, or catch fire, but will never operate again. These simulations need to be highly physics-based and capture the mechanisms by which electrons can be released or absorbed by the crystal lattice of these materials. The increasing band gaps in WBG materials like SiC and GaN increase the breakdown voltage. In addition, these materials have a smaller effective electron mass (i.e., the mass of an electron in a material dictates how fast it will move in an electric field) – which makes the switching frequency in devices based on these WBG materials faster.

A critical area of all electronics design is variability and reliability. Device performance needs to be stable and last a long time. A key factor for variability and reliability is defects in the crystal lattice. These defects, or traps, act as charge centers that can drastically impact how well a device works. Simulation can also help to identify the types of traps, providing a mechanistic understanding of how the traps will impact the device physics. Recently, Synopsys issued a paper using first-principles quantum solutions to characterize specific traps in SiC with QuantumATK.

Going forward, wind energy, solar, home appliances, and even the electric grid itself are going to need new devices with different structures and materials. The future is extremely exciting for power devices, which can be found in our EVs and will soon power a huge range of applications across our society.

The post Enabling New Applications With SiC IGBT And GaN HEMT For Power Module Design appeared first on Semiconductor Engineering.

The need to mitigate climate change is driving a need to electrify our infrastructure, vehicles, and appliances, which can then be charged and powered by renewable energy sources. The most visible and impactful electrification is now under way for electric vehicles (EVs). Beyond the transition to electric engines, several new features and technologies are driving the electrification of vehicles. The number of sensors in a vehicle is skyrocketing, driven by autonomous driving and other safety features, while a modern software-defined vehicle (SDV) is electrifying everything from air-conditioned seats to self-parking technology.

An important technology for EVs and SDVs is power modules. These are super high-voltage devices that convert one form of electricity to another (e.g., AC to DC), which is necessary to convert the vehicle battery energy to a current that can run the vehicles electrical system, including the drive train. These modules demand the highest power loads and are rated at 1000s of voltages – and the design of power devices, which are the fundamental electronic component of the power modules, is crucial, as a bad design can lead to catastrophe events.

Power devices, much more than other types of electrical devices, are designed for specific applications. In comparison, logic transistors can be used in everything from toasters to smartphones. Not only does the architecture of power devices change at higher voltages, different power ratings, or higher switching frequencies as needed, but the material can change as well.

New power requirements need wide-band gap materials

To meet new and future power demands for EVs, electric infrastructure, and other novel electrical systems, wide-band gap (WBG) materials are being developed and introduced. Silicon carbide (SiC) IGBTs are now available and being deployed, while gallium arsenide (GaN) HEMTs are a promising technology that is in the development stage.

Power density vs. switching frequency of power devices based on different materials.

Continuing with our EV example, SiC inverters can generally increase the potential range by approximately 10%, even after accounting for other design considerations. In addition, increasing the drive train voltage from 400V range to 800V can reduce the charging speeds by half. These voltages are only possible to realize with wide-band gap materials like SiC-based power devices. Tesla introduced SiC MOSFETs into its Model S back in 2018. Since then, numerous automotive manufacturers have also adopted SiC in their EVs, including Hyundai and BMW, for example.

GaN still has many design hurdles to overcame to improve reliability and decrease cost – but if it can be made affordable, perhaps the next realization of EVs will allow for charging in seconds with ranges of thousands of miles.

Simulating power devices

Because of the huge number of design parameters, simulation is important in the design of power devices. One crucial part for device design is the calculation of the breakdown voltage – the voltage at which the device can essentially melt, or catch fire, but will never operate again. These simulations need to be highly physics-based and capture the mechanisms by which electrons can be released or absorbed by the crystal lattice of these materials. The increasing band gaps in WBG materials like SiC and GaN increase the breakdown voltage. In addition, these materials have a smaller effective electron mass (i.e., the mass of an electron in a material dictates how fast it will move in an electric field) – which makes the switching frequency in devices based on these WBG materials faster.

A critical area of all electronics design is variability and reliability. Device performance needs to be stable and last a long time. A key factor for variability and reliability is defects in the crystal lattice. These defects, or traps, act as charge centers that can drastically impact how well a device works. Simulation can also help to identify the types of traps, providing a mechanistic understanding of how the traps will impact the device physics. Recently, Synopsys issued a paper using first-principles quantum solutions to characterize specific traps in SiC with QuantumATK.

Going forward, wind energy, solar, home appliances, and even the electric grid itself are going to need new devices with different structures and materials. The future is extremely exciting for power devices, which can be found in our EVs and will soon power a huge range of applications across our society.

The post Enabling New Applications With SiC IGBT And GaN HEMT For Power Module Design appeared first on Semiconductor Engineering.

Researchers at Oak Ridge National Laboratory in Tennessee recently announced that they have set a record for wireless EV charging. Their system’s magnetic coils have reached a 100-kilowatt power level. In tests in their lab, the researchers reported their system’s transmitter supplied enough energy to a receiver mounted on the underside of a Hyundai Kona EV to boost the state of charge in the car’s battery by 50 percent (enough for about 150 kilometers of range) in less than 20 minutes.

“Impressive,” says Duc Minh Nguyen, a research associate in the Communication Theory Lab at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. Nguyen is the lead author of several of papers on dynamic wireless charging, including some published when he was working toward his PhD at KAUST.

In 15 minutes, “the batteries could take on enough energy to drive for another two-and-a-half or three hours—just in time for another pit stop.”
–Omer Onar, Oak Ridge National Laboratory

The Oak Ridge announcement marks the latest milestone in work on wireless charging that stretches back more than a decade. As IEEE Spectrum reported in 2018, WiTricity, headquartered in Watertown, Mass., had announced a partnership with an unspecified automaker to install wireless charging receivers on its EVs. Then in 2021, the company revealed that it was working with Hyundai to outfit some of its Genesis GV60 EVs with Wireless charging. (In early 2023, Car Buzz reported that it had sniffed out paperwork pointing to Hyundai’s plans to equip its Ionic 5 EV with wireless charging capability.)

The plan, said WiTricity, was to equip EVs with magnetic resonance charging capability so that if such a vehicle were parked over a static charging pad installed in, say, the driver’s garage, the battery would reach full charge overnight. By 2020, we noted, a partnership had been worked out between Jaguar, Momentum Dynamics, Nordic taxi operator Cabonline, and charging company Fortam Recharge. That group set out to outfit 25 Jaguar I-Pace electric SUVs with Momentum Dynamics’ inductive charging receivers. The receivers and transmitters, rated at 50 to 75 kilowatts, were designed so that any of the specially equipped taxis would receive enough energy for 80 kilometers of range by spending 15 minutes above the energized coils embedded in the pavement as the vehicle works its way through a taxi queue. Now, according to Oak Ridge, roughly the same amount of charging time will yield about 1.5 times that range.

The Oak Ridge research team admits that installing wireless charging pads is expensive, but they say dynamic and static wireless charging can play an important role in expanding the EV charging infrastructure.

This magnetic resonance transmitter pad can wirelessly charge an EV outfitted with a corresponding receiver.Oak Ridge National Laboratory

Omad Onar, an R&D staffer in the Power Electronics and Electric Machinery Group at Oak Ridge and a member of the team that developed the newest version of the wireless charging system, envisions the static versions of these wireless charging systems being useful even for extended drives on highways. He imagines them being placed under a section of specially marked parking spaces that allow drivers to pull up and start charging without plugging in. “The usual routine—fueling up, using the restroom, and grabbing coffee or a snack usually takes about 15 minutes or more. In that amount of time, the batteries could take on enough energy to drive for another two-and-a-half or three hours—just in time for another pit stop.” What’s more, says Onar, he and his colleagues are still working to refine the system so it will transfer energy more efficiently than the one-off prototype they built in their lab.

Meanwhile, Israeli company Electreon has already installed electrified roads for pilot projects in Sweden, Norway, Italy, and other European countries, and has plans for similar projects in the United States. The company found that by installing a stationary wireless charging spot at one terminal end of a bus route near Tel Aviv University (its first real-world project), electric buses operating on that route were able to ferry passengers back and forth using batteries with one-tenth the storage capacity that was previously deemed necessary. Smaller batteries mean cheaper vehicles. What’s more, says Nguyen, charging a battery in short bursts throughout the day instead of depleting it and filling it with up with, say, an hour-long charge at a supercharging station extends the battery’s life.

Stephen Cass: Hi. I’m Stephen Cass, a senior editor at IEEE Spectrum. And welcome to Fixing The Future, our bi-weekly podcast that focuses on concrete solutions to hard problems. Before we start, I want to tell you that you can get the latest coverage from some of Spectrum‘s most important beats, including AI, climate change, and robotics, by signing up for one of our free newsletters. Just go to spectrum.ieee.org/newsletters to subscribe.

Today on Fixing The Future, we’re doing something a little different. Normally, we deep dive into exploring one topic, but that does mean that some really interesting things get left out for the podcast simply because they wouldn’t take up a whole episode. So here today to talk about some of those interesting things, I have Spectrum‘s Editor in Chief Harry Goldstein. Hi, boss. Welcome to the show.

Harry Goldstein: Hi there, Stephen. Happy to be here.

Cass: You look thrilled.

Goldstein: I mean, I am thrilled. I’m always excited to talk about Spectrum stories.

Cass: No, we’ve tied you down and made you agree to this, but I think it’ll be fun. So first up, I’d like to talk about this guest post we had from Bert Hubert which seemed to really strike a chord with readers. It was called Why Bloat Is Still Software’s Biggest Vulnerability: A 2024 plea for lean software. Why do you think this one resonated with readers, and why is it so important?

Goldstein: I think it resonated with readers because software is everywhere. It’s ubiquitous. The entire world is essentially run on software. A few days ago, even, there was a good example of the AT&T network going down likely because of some kind of software misconfiguration. This happens constantly. In fact, it’s kind of like bad weather, the software systems going down. You just come to expect it, and we all live with it. But why we live with it and why we’re forced to live with it is something that people are interested in finding out more, I guess.

Cass: So I think, in the past, when we associated giant bloated software, we had associated with large projects, these big government projects, these big airlines, big, big, big projects. And we’ve written about that a lot at Spectrum before, haven’t we?

Goldstein: We certainly have. And Bob Charette, our longtime contributing editor, who is actually the father of lean software, back in the early ‘90s took the Toyota Total Quality Management program and applied it to software development. And so it was pretty interesting to see Hubert’s piece on this more than 30 years later where the problems have just proliferated. And think about your average car these days. It’s approaching a couple hundred million lines of code. A glitch in any of those could cause some kind of safety problem. Recalls are pretty common. I think Toyota had one a few months ago. So the problem is everywhere, and it’s just going to get worse.

Cass: Yeah. One of the things that struck me was that Bert’s making the argument that you don’t actually need now an army of programmers to create bloated software— to get all those millions of lines of code. You could be just writing a code to open a garage door. This is a trivial program. Because of the way you’re writing it on frameworks, and those are pulling in dependencies and so on, you’re pulling in just millions of lines of other people’s code. You might not even know you’re doing it. And you kind of don’t notice unless, at the end of the day, you look at your final program file and you’re like, “Oh, why is that megabytes upon megabytes?” which represents endless lines of source code. Why is that so big? Because this is how you do software. You just pull these things together. You glue stuff. You focus on the business logic because that’s your value add, but you’re not paying attention to this enormous sort of—I don’t know; what would you call it?—invisible dark matter that surrounds your software.

Goldstein: Right. It’s kind of like dark matter. Yeah, that’s kind of true. I mean, it actually started making me think. All of these large language models that are being applied to software development. Co-piloting, I guess they call it, right, where the coder is sitting with an AI, trying to write better code. Do you think that might solve the problem or get us closer?

Cass: No, because I think those systems, if you look at them, they reflect modern programming usage. And modern programming usage is often to use the frameworks that are available. It’s not about really getting in and writing something that’s a little bit leaner. Actually, I think the Ais—it’s not their fault—they just do what we do. And we write bloaty softwares. So I think that’s not going to get any better necessarily with this AI stuff because the point of lean software is it does take extra time to make, and there are no incentives to make lean software. And Bert talks about, “Maybe we’re going to have to impose some of this legis— l e g i s l a tively.”—I speak good. I editor. You hire wise.—But some of these things are going to have to be mandated through standards and regulations, and specifically through the lens of these cybersecurity requirements and knowing what’s going into your software. And that may help with all just getting a little bit leaner. But I did actually want to— another news story that came up this week was Apple closing down its EV division. And you mentioned Bob Charette there. And he wrote this great thing for us recently about why EV cars are one thing and EV infrastructure is an even bigger problem and why EVs are proving to be really quite tough. And maybe the problem— again, it’s a dark matter problem, not so much the car at the center, but this sort of infrastructure— just talk a little bit about Bob’s book, which is, by the way, free to download, and we’ll have the link in the show notes.

Goldstein: Everything you need to know about the EV transition can be yours for the low, low price of free. But, yeah. And I think we’re starting to see-- I mean, even if you mandate things, you’re going to-- you were talking about legislation to regulate software bloat.

Cass: Well, it’s kind of indirect. If you want to have good security, then you’re going to have to do certain things. The White House just came out with this paper, I think yesterday or the day before, saying, “Okay, you need to start using memory-safe languages.” And it’s not quite saying, “You are forbidden from using C, and you must use Rust,” but it’s kind of close to that for certain applications. They exempted certain areas. But you can see, that is the government really coming in and, actually, what has often been a very personal decision of programmers, like, “What language do I use?” and, “I know how to use C. I know how to do garbage collection,” the government kind of saying, “Yeah, we don’t care how great a programmer you think you are. These programs lead to this class of bugs, and we’d really prefer if you used one of these memory-safe languages.” And that’s, I guess, a push into sort of the private lives of programmers that I think we’re going to see more of as time goes by.

Goldstein: Oh, that’s interesting because the—I mean, where I was going with that connection to legislation is that—I think what Bob found in the EV transition is that the knowledge base of the people who are charged with making decisions about regulations is pretty small. They don’t really understand the technology. They certainly don’t understand the interdependencies, which are very similar to the software development processes you were just referring to. It’s very similar to the infrastructure for electric cars because the idea, ultimately, for electric cars is that you also are revamping your grid to facilitate, whatchamacallit, intermittent renewable energy sources, like wind and solar, because having an electric car that runs off a coal-fired power plant is defeating the purpose, essentially. In fact, Ozzie Zehner wrote an article for us way back in the mid-Teens about the— the dirty secret behind your electric car is the coal that fuels it. And—

Cass: Oh, that was quite controversial. Yeah. I think maybe because the cover was a car perched at the top of a giant mountain of coal. I think that—

Goldstein: But it’s true. I mean, in China, they have one of the biggest electric car industries in the world, if not the biggest, and one of the biggest markets that has not been totally saturated by personal vehicles, and all their cars are going to be running on coal. And they’re the world’s second-largest emitter behind the US. But just circling back to the legislative angle and the state of the electric vehicle industry-- well, actually, are we just getting way off topic with the electric vehicles?

Cass: No, it is this idea of interdependence and these very systems that are all coupled in all kinds of ways we don’t expect. And with that EV story— so last time I was home in Ireland, one of the stories was— so they had bought this fleet of buses to put in Dublin to replace these double-decker buses, electric double-deck, to help Ireland hit its carbon targets. So this was an official government goal. We bought the buses, great expense purchasing the buses, and then they can’t charge the buses because they haven’t already done the planning permission to get the charging stations added into the bus depot, which just was this staggering level of interconnect whereas, one hand, the national government is very— “Yes, meeting our target goals. We’re getting these green buses in. Fantastic advance. Very proud of it,” la la la la, and you can’t plug the things in because just the basic work on the ground and dealing with the local government has not been there to put in the charging stations. All of these little disconnects add up. And the bigger, the more complex system you have, the more these things add up, which I think does come back to lean software. Because it’s not so much, “Okay. Yeah, your software is bloaty.” Okay, you don’t win the Turing Prize. Boo-hoo. Okay. But the problem is that because you are pulling all of these dependencies that you just do not know and all these places where things break— or the problem of libraries getting hijacked.

So we have to retain the capacity on some level— and this actually is a personal thing with me, is that I believe in the concept of personal computing. And this was the thing back in the 1970s when personal computers first came out, which the idea was it would— it was very explicitly part of the culture that you would free yourself from the utilities and the centralized systems and you could have a computer on your desk that will let you do stuff, that you didn’t have to go through, at that stage, university administrators and paperwork and you could— it was a personal computer revolution. It was very much front and center. And nowadays it’s kind of come back full circle because now we’re increasingly finding things don’t work if they’re not network connected. So I believe it should be possible to have machines that operate independently, truly personal machines. I believe it should be possible to write software to do even complicated things without relying on network servers or vast downloads or, again, the situation where you want it to run independently, okay, but you’ve got to download these Docker images that are 350 megabytes or something because an entire operating system has to be bundled into them because it is impossible to otherwise replicate the correct environment in which software is running, which also undercuts the whole point of open source software. The point of open source is, if I don’t like something, I can change it. But if it’s so hard for me to change something because I have to replicate the exact environment and toolchains that people on a particular project are using, it really limits the ability of me to come in and maybe— maybe I just want to make some small changes, or I just want to modify something, or I want to pull it into my project. That I have to bring this whole trail of dependencies with me is really tough. Sorry, that’s my rant.

Goldstein: Right. Yeah. Yeah. Actually, one of the things I learned the most about from the Hubert piece was Docker and the idea that you have to put your program in a container that carries with it an entire operating system or whatever. Can you tell me more about containers?

Cass: Yeah. Yeah. Yeah. I mean, you can put whatever you want into a container, and some containers are very small. It distributes its own thing. You can get very lean containers that is just basically the program and the install. But it basically replaces the old idea of installing software, where you’d— and that was a problem, because every time you installed a bit of software, it scarred your system in some way. There was always scar tissue because it made changes. It nestled in. If nothing else, it put files onto your disk. And so over time, one of the problems was that this then meant that your computer would accumulate random files. It was very hard to really uninstall something completely because it’d always put little hooks and would register itself in a different place in the operating system, again, because now it’s interoperating with a whole bunch of stuff. Programs are not completely standalone. At the very least, they’re talking to an operating system. You want it to talk nicely to other programs in the operating system. And this led to all these kind of direct install problems.

And so the idea was, “Oh, we will sandbox this out. We’ll have these little Docker images, basically, to do it,” but that does give you the freedom whereby you can build these huge images, which are essentially virtual machines running away. So, again, it relieves the process of having to figure out your install and your configuration, which is one thing he was talking about. When you had to do these installers, it did really make you clarify your thinking very sharply on configuration and so on. So again, containers are great. All these cloud technologies, being able to use libraries, being able to automatically pull in dependencies, they’re all terrific in moderation. They all solve very real problems. I don’t want to be a Luddite and go, “We should go back to writing assembler code as God intended.” That’s not what I’m saying, but we do sometimes have to look at— it does sometimes enable bad habits. It can incentivize bad habits. And you have to really then think very deliberately about how to combat those problems as they pop up.

Goldstein: But from the beginning, right? I mean, it seems to me like you have to commit to a lean methodology at the start of any project. It’s not something that the AI is going to come in and magically solve and slim down at the end.

Cass: No, I agree. Yeah, you have to commit to it, or you have to commit to frameworks where— I’m not going to necessarily use these frameworks. I’m going to go and try and do some of this myself, or I’m going to be very careful in how I look at my frameworks, like what libraries I’m going to use. I’m going to use maybe a library that doesn’t pull in other dependencies. This guy maybe wrote this library which has got 80 percent of what I need it to do, but it doesn’t pull in libraries, unlike the bells and whistles thing which actually does 400 percent of what I need it to do. And maybe I might write that extra 20 percent. And again, it requires skill and it requires time. And it’s like anything else. There are just incentives in the world that really tend to sort of militate against having the time to do that, which, again, is where we start coming back into some of these regulatory regimes where it becomes a compliance requirement. And I think a lot of people listening will know that time when things get done is when things become compliance requirements, and then it’s mandatory. And that has its own set of issues with it in terms of losing a certain amount of flexibility and so on, but that sometimes seems to be the only way to get things done in commercial environments certainly. Not in terms of personal projects, but certainly for commercial environments.

Goldstein: So what are the consequences, in a commercial environment, of bloat, besides— are there things beyond security? Here’s why I’m asking, because the idea that you’re going to legislate lean software into the world as opposed to having it come from the bottom up where people are recognizing the need because it’s costing them something—so what are the commercial costs to bloated software?

Cass: Well, apparently, absolutely none. That really is the issue. Really, none, because software often isn’t maintained. People just really want to get their products out. They want to move very quickly. We see this when it comes to— they like to abandon old software very quickly. Some companies like to abandon old products as soon as the new one comes out. There really is no commercial downside to using this big software because you can always say, “Well, it’s industry standard. Everybody is doing it.” Because everybody’s doing it. You’re not necessarily losing out to your competitor. We see these massive security breaches. And again, the legislating for lean software is through demanding better security. Because currently, we see these huge security breaches, and there’s very minimal consequences. Occasionally, yes, a company screws up so badly that it goes down. But even so, sometimes they’ll reemerge in a different form, or they’ll get gobbled up in someone.

There really does not, at the moment, seem to be any commercial downside for this big software, in the same way that— there are a lot of weird incentives in the system, and this certainly is one of them where, actually, the incentive is, “Just use all the frameworks. Bolt everything together. Use JS Electron. Use all the libraries. Doesn’t matter because the end user is not really going to notice very much if their program is 10 megabytes versus 350 megabytes,” especially now when people are completely immune to the size of their software. Back in the days when software came on floppy disk, if you had a piece of software that came on 100 floppy disks, that would be considered impractical. But nowadays, people are downloading gigabytes of data just to watch a movie or something like this. If a program is 1 gigabyte versus 100 megabytes, they don’t really notice. I mean, the only people who notice is if, say, video games— a really big video game. And then you see people going, “Well, it took me three hours to download the 70 gigabytes for this AAA game that I wanted to play.” That’s about the only time you see people complaining about the actual storage size of software anymore, but everybody else, they just don’t care. Yeah, it’s just invisible to them now.

Goldstein: And that’s a good thing. I think Charles Choi had a piece for us on-- we’ll have endless storage, right, on disks, apparently.

Cass: Oh, I love this story because it’s another story of a technology that looks like it’s headed off into the sunset, “We’ll see you in the museum.” And this is optical disk technology. I love this story and the idea that you can— we had laser disks. We had CDs. We had CD-ROMs. We had DVD. We had Blu-ray. And Blu-ray really seemed to be in many ways the end of the line for optical disks, that after that, we’re just going to use solid-state storage devices, and we’ll store all our data in those tiny little memory cells. And now we have these researchers coming back. And now my brain has frozen for a second on where they’re from. I think they’re from Shanghai. Is it Shanghai Institute?

Goldstein: Yes, I think so.

Cass: Yes, Shanghai. There we go. There we go. Very nice subtle check of the website there. And it might let us squeeze this data center into something the size of a room. And this is this optical disk technology where you can make a disk that’s about the size of just a regular DVD. And you can squeeze just enormous amount of data. I think he’s talking about petabits in a—

Goldstein: Yeah, like 1.6 petabits on--

Cass: Petabits on this optical surface. And the magic key is, as always, a new material. I mean, we do love new materials because they’re always the wellspring from which so much springs. And we have at Spectrum many times chased down materials that have not fulfilled necessarily their promise. We have a long history— and sometimes materials go away and they come back, like—

Goldstein: They come back, like graphene. It’s gone away. It’s come back.

Cass: —graphene and stuff like this. We’re always looking for the new magic material. But this new magic material, which has this—

Goldstein: Oh, yeah. Oh, I looked this one up, Stephen.

Cass: What is it? What is it? What is it? It is called--

Goldstein: Actually, our story did not even bother to include the translation because it’s so botched. But it is A-I-E, dash, D-D-P-R, AIE-DDPR or aggregation-induced emission dye-doped photoresist.

Cass: Okay. Well, let’s just call it magic new dye-doped photoresist. And the point about this is that this material works at basically four wavelengths. And why you want a material that responds at four different wavelengths? Because the limit on optical technologies— and I’m also stretching here into the boundaries on either side of optical. The standard rule is you can’t really do anything that’s smaller than the wavelength of the light you’re using to read or write. So the length of your laser sets the density of data on your disk. And what these clever clogs have done is they’ve worked out that by using basically two lasers at once, you can, in a very clever way, write a blob that is smaller than the wavelength of light, and you can do it in multiple layers. So usually, your standard Blu-ray disk, they’re very limited in the number of layers they have on them, like CDs originally, one layer.

So you have multiple layers on this disk that you can write to, and you can write at resolutions that you wouldn’t think you could do if you were just doing— from your high school physics or whatever. So you write it using these two lasers of two wavelengths, and then you read it back using another two lasers at two different wavelengths. And this all localizes and makes it work. And suddenly, as I say, you can squeeze racks and racks and racks of solid-state storage down to hopefully something that is very small. And what’s also interesting is that they’re actually closer to commercialization than you normally see with these early material stories. And they also think you could write one of these disks in six minutes, which is pretty impressive. As someone who stood and has sat watching the progress bars on a lot of DVD-ROMs burn over the years back in the day, six minutes to burn these—that’s probably for commercial mass production—is still pretty impressive. And so you could solve this problem of some of these large data transfers we get where currently you do have to ship servers from one side of the world to the other because it actually is too slow to copy things over the internet. And so this would increase the bandwidth of sort of the global sneakernet or station wagon net quite dramatically as well.

Goldstein: Yeah. They are super interested in seeing them deployed in big data centers. And in order for them to do that, they still have to get the writing speed up and the energy consumption down. So the real engineering is just beginning for this. Well, speaking of new materials, there’s a new use for aluminum nitride according to our colleague Glenn Zorpette who wrote about the use of the material in power transistors. And apparently, if you properly dope this material, it’ll have a much wider band gap and be able to handle higher voltages. So what does this mean for the grid, Stephen?

Cass: Yeah. So I actually find power electronics really fascinating because most of the history of transistors, right, is about making them use ever smaller amounts of electricity—5-volt logic used to be pretty common; now 3.3 is pretty common, and even 1.1 volts is pretty common—and really sipping microamps of power through these circuits. And power electronics kind of gets you back to actually the origins of being an electronics engineer, electrical engineers, which is when you’re really talking about power and energy, and you are humping around thousands of volts, and you’re humping around huge currents. And power electronics is an attempt to bring some of that smartness that transistors gives you into these much higher voltages. And we’ve seen some of this with, say, gallium nitride, which is a material we had talked about in Spectrum for years, speaking of materials that had been for years floating around, and then really, though, in the last like five years, you’ve seen it be a real commercial success. So all those wall warts we have have gotten dramatically smaller and better, which is why you can have a USB-C charger system where you can drive your laptop and bunch of ancillary peripherals all off one little wall wart without worrying about it bringing down the house because it’s just so efficient and so small. And most of those now are these new gallium-nitride-based devices, which is one example where a material really is making some progress.

And so aluminum nitride is kind of another step along that, to be able to handle even higher voltages, being able to handle bigger currents. So we’re not up yet to the level where you could have these massive high-voltage transmission lines directly, but the more and more you— the rising tide of where you can put these kind of electronics into your systems. First off, it means more efficient. As I say, these power adapters that convert AC to DC, they get more efficient. Your power supplies in your computer get more efficient, and your power supplies in your grid center. We’ve talked about how much power grid centers today get more efficient. And it bundles up. And the whole point of this is that you do want a grid that is as smart as possible. You need something that will be able to handle very intermittent power sources, fluctuating power sources. The current grid is really built around very, very stable power supplies, very constant power supplies, very stable frequency timings. So the frequency of the grid is the key to stability. Everything’s got to be on that 60 hertz in the US, 50 hertz in other places. Every power station has got to be synchronized very precisely with the other. So stability is a problem, and being able to handle fluctuations quickly is the key to both grid stability and to be able to handle some of these intermittent sources where the power varies as the wind blows stronger or weaker, as the day turns, as clouds move in front of your farm. So it’s very exciting from that point of view to see these very esoteric technologies. We’re talking about things like band gaps and how do you stick the right doping molecule in the matrix, but it does bubble up into these very-large-scale impacts when we’re talking about the future of electrical engineering and that old-school power and energy keeping the lights on and the motors churning kind of a way.

Goldstein: Right. And the electrification of everything is just going to put bigger demands on the grid, like you were saying, for alternative energy sources. “Alternative.” They’re all price competitive now, the solar and wind. But--

Cass: Yeah, not just at the generate— this idea that you have distributed power and power can be generated locally, and also being able to switch power. So you have these smart transformers so that if you are generating surplus power on your solar panels, you can send that to maybe your neighbor next door who’s charging their electric vehicle without at all having to be mediated by going up to the power company. Maybe your local transformer is making some of these local grid scale balancing decisions that are much closer to where the power is being used.

Goldstein: Oh, yeah. Stephen, that reminds me of this other piece we had this week, actually, on utilities and profit motive on their part hampering US grid expansion. It’s by a Harvard scholar named Ari Peskoe, and his first line is, “The United States is not building enough transmission lines to connect regional power networks. The deficit is driving up electricity prices, reducing grid reliability, and hobbling renewable-energy deployment.” And basically, they’re just saying that it’s not—what he does a good job explaining is not only how these new projects might impact their bottom lines but also all of the industry alliances that they’ve established over the years that become these embedded interests that need to be disrupted.

Cass: Yeah, the truth is there is a list of things we could do. Not magic things. There are pretty obvious things we could do that would make the US grid— even if you don’t care much about renewables, you probably do care about your grid resilience and reliability and being able to move power around. The US grid is not great. It is creaky. We know there are things that could be done. As a byproduct of doing those things, you also would actually make it much more renewable friendly. So it is this issue of— there are political problems. Depending on which administration is in power, there is more or less an appetite to deal with some of these interests. And then, yeah, these utilities often have incentives to kind of keep things the way they are. They don’t necessarily want a grid where it’s easier to get cheaper electricity or more green electricity from one place to a different market. Everybody loves a captive monopoly market they can sell. I mean, that’s wonderful if you could do that. And then there are many places with anti-competition rules. But grids are a real— it’s really difficult to break down those barriers.

Goldstein: It is. And if you’re in Texas in a bad winter and the grid goes down and you need power from outside but you’re an island unto yourself and you can’t import that power, it becomes something that is disruptive to people’s lives, right? And people pay attention to it during a disaster, but we have a slow-rolling disaster called climate change that if we don’t start overturning some of the barriers to electrification and alternative energy sources, we’re kind of digging our own grave.

Cass: It is very tricky because we do then get into these issues where you build these transmission lines, and there are questions about who ends up paying for those transmission lines and whether they get built over their lands, the local impacts of those. And it’s hard sometimes to tell. Is this a group that is really genuinely feeling that there is a sort of justice gap here— that they’re being asked to pay for the sins of higher carbon producers, or is this astroturfing? And sometimes it’s very difficult to tell that these organizations are being underwritten by people who are invested in the status quo, and it does become a knotty problem. And we are going to, I think, as things get more and more difficult, be really faced into making some difficult choices. And I am not quite sure how that’s going to play out, but I do know that we will keep tracking it as best we can. And I think maybe, yeah, you just have to come back and see how we keep covering the grid in pages of Spectrum.

Goldstein: Excellent. Well—

Cass: And so that’s probably a good point where— I think we’re going to have to wrap this round up here. But thank you so much for coming on the show.

Goldstein: Excellent. Thank you, Stephen. Much fun.

Cass: So today on Fixing The Future, I was talking with Spectrum‘s Editor in Chief Harry Goldstein, and we talked about electric vehicles, we talked about software bloat, and we talked about new materials. I’m Stephen Cass, and I hope you join us next time.

For more than half a century, silicon has been the bedrock of power electronics. Yet as silicon meets its physical limitations in higher-power, higher-temperature applications, the industry’s relentless pursuit of more efficient power systems has ushered in the wide bandgap (WBG) semiconductors era. The global WBG semiconductors market reached $1.6 billion in 2022, with an estimated CAGR of $13% for the next 8-year period. The adoption of WBG semiconductors, notably silicon carbide (SiC) and gallium nitride (GaN), is now setting new benchmarks for performance in power systems across automotive, industrial, and energy sectors. What impact will WBG semiconductors have on power electronics (PE) trends in 2024, and how are they redefining the design and simulation workflows for the next decade?

The catalyst for change: Wide bandgap

The term ‘bandgap’ refers to the energy difference between a material’s insulating and conducting states, a critical factor determining its electrical conductivity.

As shown in figure 1, with its wide bandgap, Gallium Nitride (GaN) exemplifies the three key advantages this property can offer.

Fig. 1: Wide bandgap semiconductor properties.

• Faster switching speeds: One of the most significant benefits of GaN’s wide bandgap is its contribution to faster switching speeds. The electron mobility in GaN is around 2,000 cm²/Vs, enabling switching frequencies up to 10 times higher than silicon. A higher switching speed translates into reduced switching losses, making the overall designs more compact and efficient.

Fig. 2: Switching speeds of SiC and GaN.

• Higher thermal resistance: With a thermal conductivity of 2 W/cmK, GaN can dissipate heat and operate at temperatures up to 200°C efficiently. This resilience enables more effective thermal management at high temperatures and extreme conditions.
• Higher voltages: With an electric breakdown field of 3.3 MV/cm, GaN can withstand almost 10 times silicon’s voltage.

GaN and other wide-bandgap semiconductors offer solutions for high-power, high-frequency, and high-temperature applications with improved energy efficiency and design flexibility.

Emerging challenges in power electronics simulation

The wider adoption of wide bandgap (WBG) semiconductors, including silicon carbide (SiC) and gallium nitride (GaN), sets new standards in the design of Switched Mode Power Supplies (SMPS) – power efficiency, compactness, and lighter weight.

However, the higher switching speeds of GaN and SiC demand more sophisticated design considerations. Power electronics engineers must manage electromagnetic interference (EMI) and optimize thermal performance to ensure reliability and functionality. Layout parasitics, for instance, can lead to voltage spikes in the presence of high di/dt values. Power electronics engineers face the following pressing questions:

• How can we guarantee reliability for mission-critical applications across a wider range of operating temperatures?
• What are the essential practices for understanding and predicting EMI and noise?
• What tools can we employ to create robust thermal models for comprehensive system-level analysis?

To navigate these complexities, engineers need advanced simulation solutions to address layout parasitic effects effectively and come with robust thermal analysis.

Fig. 3: Thermal analysis at board and schematic levels using Keysight’s PEPro.

Key impacts of WBG semiconductors: From EVs to renewable energy

Electric vehicles (EVs): As global EV sales are projected to increase by 21% in 2024, the power efficiency of automotive power electronics is paramount – every additional percentage is a big win. GaN enables more compact and efficient designs of onboard chargers and traction inverters, extending driving ranges by up to 6%.

Data centers: The digital economy’s expansion brings a surge in data center energy consumption, with the U.S. expected to require an additional 39 gigawatts over the next five years—equivalent to powering around 32 million homes. Wide bandgap semiconductors may be key to addressing this challenge by enabling higher server densities and reducing energy consumption and carbon emissions. Specifically, the implementation of GaN transistors in data center infrastructure can lead to a reduction of 100 metric tons of CO2 emissions for every 10 racks annually. This efficiency gain is particularly relevant as the computational and power demands of artificial intelligence (AI) applications soar, potentially tripling the racks’ power density.

Renewable energy: Wide bandgap semiconductors allow for more reliable power output and cost-effective solutions in both residential and commercial renewable energy storage systems. For instance, GaN transistors could achieve four times less power loss than traditional silicon-based power solutions.

The road ahead in the era of WBG semiconductors

GaN and SiC represent a new wave of material innovation to elevate the efficiencies of power electronics and redefine how we power our world. As the applications for WBG semiconductors expand, Keysight empowers our customers with a unified simulation environment to design reliable and long-lasting electronic systems under various operating conditions.

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