3 September 2019: Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA – which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications – is collaborating with Solace Power, a developer of intelligent wireless power-based solutions featuring proximity sensing and data, to enable 250W wireless power solutions designed for 5G, aerospace, automotive, medical and industrial applications. Solace Power’s intelligent wireless platform uses EPC’s 200V eGaN power transistors. This modular platform shares the same Equus architecture and enables up to 250W of transmitted power with six degrees of spatial freedom. “We’re excited to collaborate with EPC to further push the limits of our capacitive wireless power platform and to deliver previously unachievable solutions with a higher power requirement,” says Solace Power’s CEO Michael Gotlieb. “Solace focuses on delivering complete, modular systems which are pre-tested for CISPR/FCC compliance and optimized in-house for rapid development in real-world applications,” he adds. “These new solutions solve the most important challenges for applications requiring 200W or more.” For wireless power applications with higher power demands than traditional consumer devices, existing silicon-based transistors become inefficient, notes EPC. To address this limitation, Solace selected a 200V GaN-based power transistor from EPC for the 250W solution. “Wireless power is ready to be incorporated into our daily lives, and the modular platform that Solace Power has developed, using highly efficient, low-cost GaN transistors, will improve design cycle times and help new industries implement wireless power quickly and inexpensively,” says EPC’s CEO & co-founder Alex Lidow.
2 September 2019: At the International Conference on Solid State Devices and Materials (SSDM) at Nagoya University, Japan (2-5 September), Japan’s Mitsubishi Electric Corp has announced that – in collaboration with the Research Center for Ubiquitous MEMS and Micro Engineering, National Institute of Advanced Industrial Science and Technology (AIST) – it has developed what is reckoned to be the first gallium nitride high-electron-mobility transistor (GaN HEMT) with a multi-cell structure (multiple transistors cells arranged in parallel) bonded directly to a single-crystal diamond heat-dissipating substrate.
Mitsubishi Electric handled the design, manufacture, evaluation and analysis of the GaN-on-diamond HEMT and AIST developed the direct bonding technology. Part of this achievement is based on results obtained from a project commissioned by Japan’s New Energy and Industrial Technology Development Organization (NEDO). In recent years, high-power, high-efficiency GaN HEMTs have been adopted for high-power amplifiers in mobile communication base stations and satellite communications systems, helping to make such equipment smaller, lighter and more efficient. However, due to heat generation during high-power operation, the output performance inherent in GaN HEMTs cannot be realized and their reliability decreases. Most existing GaN HEMTs that use a diamond substrate for heat dissipation are created using a GaN epitaxial layer foil from which silicon substrate has been removed and onto which diamond is deposited at high temperature. HEMTs are then fabricated on the diamond substrate of the flattened GaN wafer. However, because the thermal expansion coefficients of GaN and diamond are different, the wafer can warp greatly during the manufacturing process, making it difficult to fabricate large multi-cell GaN HEMTs. In the latest research a multi-cell GaN HEMT was fabricated then the silicon substrate was removed. The back surface of the GaN HEMT was then polished to make it thinner and flatter, after which it was bonded directly onto a diamond substrate using a nano adhesion layer. A multi-cell structure was used for the parallel alignment of eight transistor cells of a type found in actual products. Finally, a multi-cell GaN-on-diamond HEMT ─ the world’s first ─ was fabricated using a substrate with high heat dissipation made of single-crystal diamond.
Using a single-crystal diamond (with high thermal conductivity of 1900W/mK) for superior heat dissipation suppresses temperature degradation, reducing the temperature rise in the GaN HEMT from 211.1°C to 35.7°C. This improves output per gate width from 2.8W/mm to 3.1W/mm as well as raising power efficiency from 55.6% to 65.2%, realizing significant energy conservation. The new GaN-on-diamond HEMT should be able to improve the power-added efficiency (PAE) of high-power amplifiers in mobile communication base stations and satellite communications systems, helping to reduce power consumption. Mitsubishi Electric aims to refine the GaN-on-diamond HEMT prior to its commercial launch, targeted for 2025.
15 August 2019: The global race to launch 5G mmWave frequencies could provide a long-anticipated market opportunity for gallium nitride (GaN) as an alternative to silicon. GaN is more power-efficient than silicon for 5G RF. In fact, GaN has been the heir apparent to silicon in 5G power amplifiers for years, especially when it comes to mmWave 5G networks. What makes it so attractive is its ability to efficiently handle higher voltage in a much smaller area than comparable laterally diffused MOSFETs (LDMOS) devices. In addition, it can power a much wider range of mmWave frequencies than standard silicon. “Most of the difference is related to the operating voltage of the transistors, where GaN can be 50V or higher and 28nm CMOS is perhaps 1.8V,” said Keith Benson, director of RF/microwave amplifier and phased array IC products at Analog Devices. “In the end, power is voltage times current, and a higher operating voltage makes high power easier. In regard to comparing GaN versus silicon, in general, that’s a complicated answer as they are very different. GaN is still expensive from a wafer cost, but the mask cost is far less than cutting-edge CMOS.”
That’s a start, but 5G has a host of problems to contend with as it scales from the sub-6GHz range into millimeter wave technology. “From a technology standpoint, 5G suffers from attenuation issues, requiring multiple antennae to improve signal quality using spatial multiplexing techniques. Each antenna requires dedicated RF front-end chipset [and power amplification],” said Ajit Paranjpe, CTO at Veeco. “Today, GaN is slowly replacing silicon in specific applications, such as the RF amplifier front-end of 4G/LTE base stations.” Next-generation designs will open the door to GaN in smaller devices—micro-cells, femto-cells and even smaller access points, although for different reasons than for higher-powered devices. “For devices with a lower power load the benefit is in the footprint, not just in board space, as well as the layout of the antenna,” Paranjpe said. “That’s where GaN offers the best fit because it operates at higher voltages.” With the big boxes, however, the issue is how much power is wasted, not only how much is used, according to Earl Lum, president of EJL Wireless Research. “Those [power amplifiers] are only maybe 30% or 35% efficient, so if you put 100 watts into it, you only get to transmit maybe 35 and the other 65 turns into heat.” At a recent conference in Shanghai, Huawei demonstrated base stations with self-contained liquid-cooling systems. That may seem like overkill, but the density of chips in base stations generates a significant amount of heat. Most other OEMs stuck to traditional methods, but there were a lot of abnormally long aluminum fins and other heat-sink mechanisms on display, Lum said. Most chipmakers responded by assuming they would be supporting both materials, though a few are pushing hard on one side or the other. Qorvo, Wolfspeed, NXP, Sumitomo and other chipmakers — especially those with experience in the microwave communications market — have promoted GaN for years as a likely successor to LDMOS in 5G base station power amplifiers (PA) and other applications. “The data demands driven by 5G and the onset of IoT will require capacity and speeds that, for example, mmWave technology can deliver,” said Gerhard Wolf, vice president and general manager for the RF product line at Wolfspeed. “GaN on silicon carbide is the optimal material for mmWave technology because of its high power density and ability to operate at high frequencies.” Cree/Wolfspeed is one of the companies making a big bet on the growth of demand for GaN-on-silicon carbide. In fact, in May it announced plans to invest $1 billion to expand its GaN-on-SiC capacity 30-fold using a redesigned, 253,000 square-foot facility currently producing 150mm wafers near its Durham, N.C., headquarters. “This is in direct answer to the demand for this next-generation technology,” Wolf said. “Today, communications infrastructure customers are rapidly pre-investing significantly in 5G ramp-up and we’re proud to be leading the charge on this movement.” Growth in sales to the defense industry, and to both the 4G and 5G mobile telco market, is forecast to drive sales of GaN components from $380 million during 2017 to $2 billion by 2024, according to a June report from Yole Développement. However, the firm noted that the vast majority of PAs in the civilian wireless market will be silicon.
The same report also predicted “remarkable progress in cost-efficient LDMOS technology,” allowing silicon to continue to challenge GaN in sub-6GHz, active-antenna and massive-MIMO implementations. That progress almost certainly would include developing standard-silicon components for mmWave networks, as longtime RF systems designer Anokiwave has done—while adding functions to reduce the effort of calibrating phased-array antennas and to reduce power use by as much as a third. “GaN is fine in isolated uses and a few high-energy applications where it is already popular — LiDAR and radar in particular,” according to Alastair Upton, Anokiwave’s chief strategy officer, who uses his company’s success at building phased-array antenna components and controllers from standard LDMOS as evidence GaN is unnecessary. “We put out our first chips at 28GHz in 2016, and with each generation we’ve gotten orders of magnitude greater efficiency in size and weight. We continue to drive the cost down at a very rapid pace.” But Upton noted that, at least for the sub-6GHz version of 5G, GaN chips will have to compete with silicon’s economies of scale with only marginal additional benefits. Good designers can get silicon to do astonishing things, but a large amplifier will dissipate heat more slowly than a small one. So GaN or anything else that can handle the same voltage as silicon in a much smaller space makes the whole process more power-efficient, said Alex Lidow, co-founder and CEO of GaN power-supply provider Efficient Power Conversion (EPC). “Gallium is a better semiconductor than silicon,” Lidow said. “That’s been well known for quite a while.” GaN traditionally has been more expensive than silicon, and when compared weight-for-weight, there is still a big difference. But the process of laying down GaN and its components epitaxially on silicon or silicon carbide brings GaN effectively up to par with silicon, and sometimes can cost slightly less, Lidow said. Analog Devices’ Benson points to a related trend. “The process technology has finally progressed to a point where it’s reliable enough to be fielded into systems,” he said. “It took more than 10 years for the fabs to eliminate many of the issues before it was ready to put into real systems.”
Unavoidable heat issues
Thermal issues are endemic to power amplifiers and RF front-ends due to the huge difference between peak and minimum power requirements, and GaN is particularly good for this. “You have to supply that same amount of power regardless if you’re transmitting at very high power, or sitting at very low power, which is much of the time, and that extra power is dissipated as heat,” said Andrew Zai, senior principal engineer at Raytheon and chair of the 5G Summit at IEEE’s recent International Microwave Symposium. “There is a technique the iPhone uses, called envelope tracking, that lets you adjust power at the level required at any instant in time rather than biasing for the worst case. But if you’re working with the amplitude modified wave form, you’re always going to have the problem of worst case vs. average.” Envelope tracking is a key functional advantage for GaN, because silicon PAs can’t switch power levels up and down quickly enough to make the technique effective, said Lidow. “Envelope tracking isn’t easy for a PA to do, because you’re adjusting to track power in real time. Silicon can’t do it quickly enough, which is why it wasn’t implemented for a long time. The big savings is not on the electric bill, though. Size is more than just a thermal issue. It can be the difference between putting a 500-pound antenna on the side of a building compared to a 50-pound antenna. That’s a big selling point.”
13 August 2019: Singapore-based IGSS GaN Pte Ltd (IGaN) – which provides proprietary gallium nitride on silicon (GaN-on-Si) epitaxial wafer fabrication services for both power and radio frequency (RF) devices – has announced its cost-effective and quick prototyping multi-project wafer (MPW) shuttle program, as it seeks to advance volume production in 200mm-diameter silicon substrates. Enabling customers to tape-out their designs for rapid prototyping, the MPW offers cost reduction through the expense sharing of masks and wafers with other MPW shuttle program partners. The service leverages the shift in demand towards GaN devices capable of improving power efficiency conversion up to 50%. “The industry is ripe for a transition to GaN devices, with various infrastructure coming together making it conducive to new technologies,” believes president George Wong. “Today, challenges around reliability have been primarily addressed, paving way for a wider adoption of GaN that is spurred by the increasingly cost-friendly manufacturing capabilities,” he adds. “This is where IGaN completes the supply chain.”
7 August 2019: The US Army recently awarded Lockheed Martin of Bethesda, MD, USA three contracts to produce additional Q-53 systems and outfit the radar with enhanced capabilities, including extended range and counter unmanned aerial system (CUAS) surveillance. The flexible architecture of the Army’s most modern radar allows for these upgrades, which support adaptable growth of the system to address aircraft, drone and other threats in the future. In use around the world since 2010, the primary mission of the Q-53 is to protect troops in combat by detecting, classifying, tracking and identifying the location of enemy indirect fire in either 90 or 360-degree modes. “The warfighter needs new and improved capabilities. The Q-53 represents a fast path to respond to current and emerging threats,” says Rick Herodes, director of the Q-53 program at Lockheed Martin. “The flexibility of the architecture continues to allow the Q-53 to provide capabilities far beyond the original mission and allows for additional upgrades in the future,” he adds. •Full-rate production – The Army awarded Lockheed Martin a contract for a third lot of 15 full-rate production systems. Once this contract is delivered, the Army will own 189 Q-53 systems. The Lot 3 systems will continue to be produced using gallium nitride (GaN) transmit-receive modules, providing the radar with additional power, reliability and the possibility for enhanced capabilities including extended range, counterfire target acquisition (CTA) and multi-mission, which delivers simultaneous CTA and air surveillance. •Surveillance – Lockheed Martin was also awarded a contract to enhance the Q-53’s CUAS capability. This true multi-mission capability delivers simultaneous counterfire, CUAS and air surveillance. •Extended range – Lockheed Martin was also awarded a contract by the Army that will extend the operating range of the Q-53 system by utilizing recent next-generation technology insertions already available in the radar. Lockheed Martin uses an open GaN foundry model, leveraging relationships with commercial suppliers that utilize the power of the expansive telecoms market to provide military-grade GaN modules while taking advantage of commercial cost efficiencies.