Tag Archives: letter-pulse-tech

The stacked color sensor


November 16, 2017

The human eye has three different types of sensory cells for the perception of colour: cells that are respectively sensitive to red, green and blue alternate in the eye and combine their information to create an overall colored image. Image sensors, for example in mobile phone cameras, work in a similar way: blue, green and red sensors alternate in a mosaic-like pattern. Intelligent software algorithms calculate a high-resolution colour image from the individual colour pixels.

However, the principle also has some inherent limitations: as each individual pixel can only absorb a small part of the light spectrum that hits it, a large part of the light is lost. In addition, the sensors have basically reached the limits of miniaturization, and unwanted image disturbances can occur; these are known as color moiré effects and have to be laboriously removed from the finished image.

Transparent only for certain colors

Researchers have therefore been working for a number of years on the idea of stacking the three sensors instead of placing them next to each other. Of course, this requires that the sensors on top let through the light frequencies that they do not absorb to the sensors underneath. At the end of the 1990s, this type of sensor was successfully produced for the first time. It consisted of three stacked silicon layers, each of which absorbed only one colour.

This actually resulted in a commercially available image sensor. However, this was not successful on the market because the absorption spectra of the different layers were not distinct enough, so part of the green and red light was absorbed by the blue-sensitive layer. The colors therefore blurred and the light sensitivity was thus lower than for ordinary light sensors. In addition, the production of the absorbing silicon layers required a complex and expensive manufacturing process.

Empa researchers have now succeeded in developing a sensor prototype that circumvents these problems. It consists of three different types of perovskites – a semiconducting material that has become increasingly important during the last few years, for example in the development of new solar cells, due to its outstanding electrical properties and good optical absorption capacity. Depending on the composition of these perovskites, they can, for example, absorb part of the light spectrum, but remain transparent for the rest of the spectrum. The researchers in Maksym Kovalenko’s group at Empa and ETH Zurich used this principle to create a color sensor with a size of just one pixel. The researchers were able to reproduce both simple one-dimensional and more realistic two-dimensional images with an extremely high color fidelity.

Accurate recognition of colors

The advantages of this new approach are clear: the absorption spectra are clearly differentiated and the colour recognition is thus much more precise than with silicon. In addition, the absorption coefficients, especially for the light components with higher wavelengths (green and red), are considerably higher in the perovskites than in silicon. As a result, the layers can be made significantly smaller, which in turn allows smaller pixel sizes. This is not crucial in the case of ordinary camera sensors; however, for other analysis technologies, such as spectroscopy, this could permit significantly higher spatial resolution. The perovskites can also be produced using a comparatively cheap process.

However, more work is still needed in order to further develop this prototype into a commercially usable image sensor. Key areas include the miniaturisation of pixels and the development of methods for producing an entire matrix of such pixels in one step. According to Kovalenko, this should be possible with existing technologies.

Perovskites are such a promising material in research that the prestigious journal Science has published a special edition about them. It includes a review article by the Empa/ETH research group led by Maksym Kovalenko about the current state of research and potential uses of lead halide perovskites nanocrystals.

These have properties that make them a promising candidate for the development of semiconductor nanocrystals for various optoelectronic applications such as television screens, LEDs and solar cells: they are inexpensive to manufacture, have a high tolerance to defects and can be tuned precisely to emit light in a specific colour spectrum.

AKHAN Semiconductor, a technology company specializing in the fabrication and application of lab-grown, electronics-grade diamond, announced today the issuance by the Japan Patent Office of a patent covering a method for the fabrication of diamond semiconductor materials, core to applications in automotive, aerospace, consumer electronics, military, defense, and telecommunications systems, amongst others.

“We are ecstatic to be awarded this key patent in Japan. Its issuance protects our proprietary interests in diamond semiconductor in one of the nations leading the globe in diamond research,” said Adam Khan, Founder & Chief Executive Officer, AKHAN Semiconductor, Inc. “Following this year’s issuances of a Taiwan diamond semiconductor patent, and a major US diamond transparent electronics patent, the Japan patent issuance is a further testament to AKHAN’s leadership in the diamond semiconductor space.”

Japan, which has actively funded millions of dollars into diamond electronics research since 2002, earlier this year announced marked progress in the development of diamond semiconductor device performance. The AKHAN granted and issued patent, JP6195831 (B2), is a foreign counterpart of other issued and pending patents owned by AKHAN Semiconductor, Inc. that are used in the company’s Miraj Diamond Platform products. As a key landmark patent, the claims protect uses far beyond the existing applications, including microprocessor applications. Covering the base materials common to nearly all semiconductor components, the intellectual property can be realized in everything from diodes, transistors, and power inverters, to fully functioning diamond chips such as integrated circuitry.

AKHAN’s flagship Miraj Diamond Glass for mobile display and camera lens is 6x stronger, 10x harder, and runs over 800x cooler than leading glass competitors like Gorilla Glass by coating standard commercial glass such as aluminosilicate, BK7, and Fused Silica with lab-grown nanocrystalline diamond. Diamond-based technology is capable of increasing power density as well as creating faster, lighter, and simpler devices for consumer use. Cheaper and thinner than its silicon counterparts, diamond-based electronics could become the industry standard for energy efficient electronics.

“This patent adds to the list of other key patents in the field of Diamond Semiconductor that are owned by the company, including the ability to fabricate transparent electronics, as well as the ability to form reliable metal contacts to diamond semiconductor systems,” said Carl Shurboff, President and Chief Operating Officer, AKHAN Semiconductor, Inc. “This patent bolsters the supporting evidence of AKHAN’s leadership in manufacturing diamond semiconductor products, and supports ongoing efforts with our major defense, aerospace and space system development partners.”

 

Seoul Semiconductor has developed an ultra-compact LED driver series with a power density 5X higher than conventional LED drivers. Based on Seoul Semiconductor’s patented Acrich technology, the MicroDriver Series delivers more than 24W of output power with a power density of 20W/cubic inch cubic inch, compared to existing drivers at 3-5W/cubic inch. Measuring just 1.5″ x 1.1″ x 0.8″ (38mm x 28mm x 20.5mm), the MicroDriver is 80% smaller than conventional LED drivers, giving lighting designers the ability to develop ultra-thin and novel luminaires with flicker-free operation.

“The new MicroDriver Series LED drivers will have a significant impact on external converters, enabling lighting design engineers to dramatically reduce the size, weight and volume of their luminaires,” explained Keith Hopwood, executive vice-president at Seoul Semiconductor. “This breakthrough in size reduction for the MicroDriver Series is the result of the company’s continuing investment in Acrich high voltage LED technology, delivering benefits for customers in smaller size, increased efficiency and lower costs.”

The MicroDriver Series LED drivers are ideal for lighting designs such as wall sconces, vanity lights, downlights, and flush-mounted lighting fixture applications. The MicroDriver Series’ smaller size facilitates the conversion of these applications to LED light sources, which was not previously possible due to bulky conventional LED drivers, making halogen lamp replacement possible without the need for a large volume recess for the driver, or a reduction in light output.

The MicroDriver Series LED drivers are ideal for luminaire designs up to 2,400 lumens, and their compact size enables integration of the lighting control circuitry with the external converter. This gives lighting designers the capability to mount more light sources on the board or reduce the total size of the fixture and mounting plate.

The resulting decrease in the LED drivers’ physical size has significant business implications for the lighting industry, giving lighting designers the ability to shrink the size of light fixtures by as much as 20%, which reduces shipping and storage costs. Because conventional LED drivers are both heavy and bulky, they are typically shipped via sea freight from manufacturers in Asia to European and North American fixture companies, with transit times up to six weeks. The MicroDriver Series LED drivers are small and lightweight enough to make airfreight practical and economical, reducing lead time and streamlining the overall supply chain.

The MicroDriver Series is rated to IP66, and is available in 10 models, rated for 8 – 24W in 120V or 230V versions, for LED assemblies from 900-2400 lumens. The drivers are CE recognized, provide flicker-free operation for phase-cut dimmers, and are compliant to California Title 24, enabling lighting designers to meet the most challenging design requirements, including low flicker, high power factor, Class B EMI and 2.5kV surge.

GLOBALFOUNDRIES and Fudan Microelectronics Group today announced they have produced a next generation dual interface CPU card, using GF’s 55nm Low Power Extended (55LPx) technology platform. GF’s 55LPx platform has the capability to integrate multiple functions onto a single chip that results in a secure, low power, and cost effective solution uniquely suited for the Chinese bank card market, including financial, social security, transportation, healthcare, and mobile payment applications.

Fudan’s dual interface CPU card, FM1280, supports both contact and contactless modes of communication, and shares a low power CPU that automatically selects the desired interface. The non-contact interface utilizes GF’s readily available and silicon-proven 55LPx RF IP. Fudan’s FM1280 also uses the embedded EEPROM-based on Silicon Storage Technology (SST) SuperFlash® memory technology to ensure user code and data security.

“With the increasing usage of smart bank cards, and in order to maintain our leadership position in this market, a solution with low power consumption was critical,” said Shen Lei, VP of Technology Engineering at Fudan.  “Our FM1280 card offers lower power consumption, enhanced reliability, and uses an advanced process node. GF’s advanced platform, 55LPx, with its low power logic and highly reliable embedded non-volatile memory, is ideal for our next generation bank card offering. Fudan is pleased to continue our long-standing relationship with GF to manufacture our industry leading products.”

The 55nm LPx platform provides a fast path-to-product solution, and includes SST’s SuperFlash® memory technology, which is fully qualified for consumer, industrial and automotive applications. GF’s 55LPx implementation of SuperFlash offers a small bitcell size, very fast read speed, and superior data retention and endurance.

“GF is delighted to expand our relationship with Fudan Microelectronics, who is the acknowledged leader in the Chinese smart card industry,” said Dave Eggleston, vice president of Embedded Memory at GF. “Fudan joins our rapidly growing customer base for GF’s 55LPx platform, which offers a superior combination of low power logic, embedded non-volatile memory and RF IP for the smart card, wearable IoT, industrial MCU and automotive markets.”

GF’s 55LPx-enabled platform is in volume production at the foundry’s 300mm line in Singapore. GF has previously announced that On Semiconductor and Silicon Mobility are currently using GF’s 55LPx platform for wearable IoT and automotive products.

Ben-Gurion University of the Negev (BGU) researchers have achieved a breakthrough in manipulating light to render an object, such as an optical chip, invisible.

According to the recent study published in Nature Scientific Reports, the researchers conceived a new method that deflects and scatters light away from a “cloaking” chip surface so it is not detected.

An operational cloaking chip can be an extension of the basic technologies such as radar-absorbing dark paint used on stealth aircraft, local optical camouflage, surface cooling to minimize electromagnetic infrared emissions, or electromagnetic wave scattering.

“These results open the door to new integrated photonic devices, harnessing electromagnetic fields of light at nanoscale for a variety of applications from on-chip optical devices to all-optical processing,” says Dr. Alina Karabchevsky, head of BGU’s Light-on-a-Chip Group and a member of the BGU Unit of Electro-Optical Engineering and the Ilse Katz Institute for Nanoscale Science and Technology. “We showed that it is possible to bend the light around an object located on the cloak on an optical chip. The light does not interact with the object, thus resulting in the object’s invisibility.”

The next step is for researchers to overcome the significant challenge of developing a prototype.

Other group researchers who contributed to the study, Invisibility Cloaking Scheme by Evanescent Fields Distortion on Composite Plasmonic Waveguides with Si Nano-Spacer, include Yakov Galutin, an MSc student and a member of the BGU Electro-Optical Engineering Unit and the Ilse Katz Institute for Nanoscale Science and Technology, and Eran Falek, a student in the Department of Electrical and Computer Engineering.

Electrical physicists from Czech Technical University have provided additional evidence that new current sensors introduce errors when assessing current through iron conductors. It’s crucial to correct this flaw in the new sensors so that operators of the electrical grid can correctly respond to threats to the system. The researchers show how a difference in a conductor’s magnetic permeability, the degree of material’s magnetization response in a magnetic field, affects the precision of new sensors. They also provide recommendations for improving sensor accuracy. The results are published this week in AIP Advances, from AIP Publishing.

With the addition of new renewable energy sources and smart homes demanding more information, the electrical grid is becoming more complex. Author Pavel Ripka said, “If you have [a] grid at the edge of capacity, you have to be careful to monitor all the transients (power surges).” Surges are overloads or failures to the system, which can be caused by something as simple as a broken power line, or more dramatic events like lightning strikes or geomagnetic storms.

Ripka explained the importance of monitoring electrical currents: “Every day you get a lot of these small events (surges) within a big power grid, and sometimes it is difficult to interpret them. If it is something really serious, you should switch off parts of the grid to prevent catastrophic damage, but if it’s a short transient which will finish fast there is no need to disconnect the grid. It’s a risky business to distinguish between these events, because if you underestimate the danger then parts of the distribution installations can be damaged causing serious blackouts. But if you overestimate and disconnect, it is a problem because connecting these grids back together is quite complicated,” he said.

To address the increasing complexity of the grid and power outage threats, there has been an increase in use of ground current sensors in the past couple of years. New yokeless current sensors are popular because of their low cost and compact size. These sensors are good for assessing currents in nonmagnetic conductors such as copper and aluminum. However, ground conductors are usually iron due to its mechanical strength, and iron has a high magnetic permeability.

Using these new sensors to measure ground currents when iron is present is a bit like using a thermometer to assess if the heating needs to be switched on, not taking into account where exactly the thermometer is placed. Near a door or window, the thermometer’s reading can be affected differently than elsewhere. In the same way, this study has shown that not taking into account the magnetic permeability of a conductor distorts the accuracy of a reading with a yokeless sensor.

Ripka and his team matched experimental measurements with theoretical simulations to highlight the difference in yokeless sensor readings between nonmagnetic and magnetic conductors.

“We can show how to design (yokeless) current sensors so that they are not so susceptible to this type of error,” Ripka said. “[This study is] just a small reminder to make [engineers] design sensors safely.”

To further prove the point, Ripka’s group is starting to take long-term readings at power stations, comparing results to commercial uncalibrated sensors. In the future, Ripka envisions cooperating with geophysicists to correlate ground currents and geomagnetic activity, to better understand how these currents are distributed within the earth and even predict future disruptions to the grid.

Seoul Semiconductor exhibited its new SunLike Series LEDs, the world’s first LED to produce light that closely matches the spectrum of natural sunlight, at the recent Professional Lighting Design Conference (PLDC), held in Paris, France from Nov. 1 – 4. The new LED technology, first unveiled in Frankfurt, Germany in June of this year, is generating interest from many global lighting companies, who are developing new lighting products using SunLike Series LEDs.

New products from leading lighting designers powered by Seoul Semiconductor’s SunLike LED technology were on display at PLDC 2017, which attracted more than 2000 attendees. A number of these companies signaled their intention to launch these new SunLike-powered lighting products in the market.

The director of Seoul Semiconductor’s Lighting Divison, Mr. Yo Cho, was invited as a keynote speaker at the PLDC’s opening event, where he presented SunLike Series LED technology. “Because the SunLike Series LEDs are designed to deliver light that closely matches sunlight’s natural spectrum, they provide an optimized light source that maximizes the benefits of natural light,” said Mr. Cho. “Thus, the colors and texture of objects can be viewed more accurately, as they would be seen under natural sunlight.”

According to Dr. Kibum Nam, head of Seoul Semiconductor R&D Center and Chief Technology Officer, “SunLike Series LEDs have the potential to drive a revolution in lighting – overcoming the limits of artificial light sources by implementing light closer to the natural spectrum of sunlight. Seoul will open a new era of natural spectrum lighting with the launch of more SunLike LED technology.”

SunLike Series natural spectrum LEDs may also play a key role in minimizing the negative effects of artificial lighting. While conventional LED technology produces light with a pronounced blue “spike” in its spectral output, SunLike LEDs implement a more uniform spectrum that more closely matches natural sunlight, lowering this blue light spike. Some recent research indicates that this blue light spike may produce negative effects when viewed for prolonged periods of time during night-time hours, potentially interfering with natural human biorhythms. By employing new light sources powered by SunLike Series LEDs, lighting designers will be able to deliver a healthier light experience.

Interest in the link between light sources and human health is higher than ever before, as evidenced by the winners of this year’s Nobel Prize in Physiology, Professor Jeffrey C. Hall, University of Maine; Professor Michael Morris Rosbach, Brandeis University; and Professor Michael Young, Rockefeller University. These researchers are credited with seminal discoveries about the cellular mechanisms for circadian biology.

At the SC17 show, Micron Technology, Inc., (Nasdaq:MU) today announced a new 32GB NVDIMM-N offering twice the capacity of existing NVDIMMs, providing system designers and original equipment manufacturers (OEMs) with new flexibility to work with larger data sets in fast persistent memory.

The solution is architected to support the increasing performance, energy efficiency and uptime requirements of data analytics and online transaction processing applications. Compared to server configurations using traditional far storage, deploying NVDIMMs can deliver up to 400 percent performance benefits.

As data center storage volumes grow, database queries increasingly need key datasets to be retained in-memory to improve access speeds due to the rising business requirement for higher availability. Many businesses are seeing increased value in placing fast memory near the processor to reduce the need to transfer data from far storage.

Persistent memory delivers a unique balance of latency, bandwidth, capacity and cost by delivering ultra-fast DRAM speeds for critical data. What sets it apart from standard server DRAM is its ability to preserve information in the event of a power loss. Micron’s technology provides a unique solution for near-memory data analysis and addresses rising bandwidth demands of data-rich applications in markets such as finance, medicine, retail, and oil and gas exploration.

NVDIMM has emerged as a critical persistent memory technology due to its ability to deliver the performance levels of DRAM combined with the persistent reliability of NAND. It reduces the bandwidth gap between memory and storage.

Applications which require frequent updates — such as journaling or transactional logging of metadata — now have the capability to leverage NVDIMM for these functions instead of traditional far storage. Micron’s NVDIMM allows customers to raise read-centric performance by 11 percent and write-centric performance by 63 percent for block level data.

“As data sets get larger and larger, data access becomes increasingly critical to application performance,” said Tom Eby, senior vice president for Micron’s Compute and Networking Business Unit. “Our new 32GB NVDIMM-N equips system architects with a high-capacity persistent memory solution that can dramatically increase throughput and improve total cost of ownership.”

VMware and Dell are collaborating with Micron to increase the performance for virtualized applications. With virtual persistent memory, customers can now run multiple operating systems in a virtualized environment while reducing overall network traffic.

“As the global leader in cloud infrastructure and business mobility, VMware recognized early the significant reduction of database and local storage latencies that Micron NVDIMM-N can bring to our virtualized customers using Dell PowerEdge servers,” said Richard A. Brunner, chief platform architect and vice president of Server Platform Technologies at VMware, Inc. “Using the 16 GB NVDIMM-N from Micron for the Dell PowerEdge 14G servers, a future version of VMware vSphere(R) intends to efficiently grow the number and size of virtualized persistent memory workloads in the data center while ensuring the benefits of live migration, check-pointing, and legacy storage optimizations for NVDIMM. VMware looks forward to the improvements that can arise when the server industry starts deploying the new 32 GB Micron NVDIMM-N to our customers.”

“Persistent memory solutions enables our customers to optimize intensive database and analytics workloads,” said Robert Hormuth, vice president and fellow, Server Division CTO at Dell EMC. “Micron’s advancement in persistent memory offering and Dell EMC engineering efforts to enhance NVDIMM capability of PowerEdge servers will boost application performance, reduce system crash recovery time and enhance SSD endurance for our customers.”

The trick is to be able to use beryllium atoms in gallium nitride. Gallium nitride is a compound widely used in semiconductors in consumer electronics from LED lights to game consoles. To be useful in devices that need to process considerably more energy than in your everyday home entertainment, though, gallium nitride needs to be manipulated in new ways on the atomic level.

“There is growing demand for semiconducting gallium nitride in the power electronics industry. To make electronic devices that can process the amounts of power required in, say, electric cars, we need structures based on large-area semi-insulating semiconductors with properties that allow minimising power loss and can dissipate heat efficiently. To achieve this, adding beryllium into gallium nitride – or ‘doping’ it – shows great promise,” explains Professor Filip Tuomisto from Aalto University.

Sample chamber of the positron accelerator. Credit: Hanna Koikkalainen

Sample chamber of the positron accelerator. Credit: Hanna Koikkalainen

Experiments with beryllium doping were conducted in the late 1990s in the hope that beryllium would prove more efficient as a doping agent than the prevailing magnesium used in LED lights. The work proved unsuccessful, however, and research on beryllium was largely discarded.

Working with scientists in Texas and Warsaw, researchers at Aalto University have now managed to show – thanks to advances in computer modelling and experimental techniques – that beryllium can actually perform useful functions in gallium nitride. The article published in Physical Review Letters shows that depending on whether the material is heated or cooled, beryllium atoms will switch positions, changing their nature of either donating or accepting electrons. “Our results provide valuable knowledge for experimental scientists about the fundamentals of how beryllium changes its behaviour during the manufacturing process. During it – while being subjected to high temperatures – the doped compound functions very differently than the end result,” describes Tuomisto.

If the beryllium-doped gallium nitride structures and their electronic properties can be fully controlled, power electronics could move to a whole new realm of energy efficiency.

“The magnitude of the change in energy efficiency could as be similar as when we moved to LED lights from traditional incandescent light bulbs. It could be possible to cut down the global power consumption by up to ten per cent by cutting the energy losses in power distribution systems,” says Tuomisto.

Researchers have developed a technique that allows users to collect 100 times more spectrographic information per day from microfluidic devices, as compared to the previous industry standard. The novel technology has already led to a new discovery: the speed of mixing ingredients for quantum dots used in LEDs changes the color of light they emit – even when all other variables are identical.

Researchers have discovered that the speed of mixing ingredients for quantum dots used in LEDs changes the color of light they emit -- even when all other variables are identical. Credit: Milad Abolhasani

Researchers have discovered that the speed of mixing ingredients for quantum dots used in LEDs changes the color of light they emit — even when all other variables are identical. Credit: Milad Abolhasani

“Semiconductor nanocrystals are important structures used in a variety of applications, ranging from LED displays to solar cells. But producing nanocrystalline structures using chemical synthesis is tricky, because what works well on a small scale can’t be directly scaled up – the physics don’t work,” says Milad Abolhasani, an assistant professor of chemical and biomolecular engineering at North Carolina State University and corresponding author of a paper on the work.

“This challenge has led to an interest in continuous nanomanufacturing approaches that rely on precisely controlled microfluidic-based synthesis,” Abolhasani says. “But testing all of the relevant variables to find the best combination for manufacturing a given structure takes an extremely long time due to the limitations of the existing monitoring technologies – so we decided to build a completely new platform.”

Currently, microfluidic monitoring technologies are fixed in place, and monitor either absorption or fluorescence. Fluorescence data tells you what the crystal’s emission bandgap is – or what color of light it emits – which is important for LED applications. Absorption data tells you the crystal’s size and concentration, which is relevant for all applications, as well as its absorption bandgap – which is important for solar cell applications.

To monitor both fluorescence and absorption you’d need two separate monitoring points. And, being fixed in place, people would speed up or slow down the flow rate in the microfluidic channel to control the reaction time of the chemical synthesis: the faster the flow rate, the less reaction time a sample has before it hits the monitoring point. Working around the clock, this approach would allow a lab to collect about 300 data samples in 24 hours.

Abolhasani and his team developed an automated microfluidic technology called NanoRobo, in which a spectrographic monitoring module that collects both fluorescent and absorption data can move along the microfluidic channel, collecting data along the way. The system is capable of collecting 30,000 data samples in 24 hours – expediting the discovery, screening, and optimization of colloidal semiconductor nanocrystals, such as perovskite quantum dots, by two orders of magnitude. Video of the automated system can be seen at https://www.youtube.com/watch?v=FBQoSDdn_Uk.

And, because of the translational capability of the novel monitoring module, the system can study reaction time by moving along the microfluidic channel, rather than changing the flow rate – which, the researchers discovered, makes a big difference.

Because NanoRobo allowed researchers to monitor reaction time and flow rate as separate variables for the first time, Abolhasani was the first to note that the velocity of the samples in the microfluidic channel affected the size and emission color of the resulting nanocrystals. Even if all the ingredients were the same, and all of the other conditions were identical, samples that moved – and mixed – at a faster rate produced smaller nanocrystals. And that affects the color of light those crystals emit.

“This is just one more way to tune the emission wavelength of perovskite nanocrystals for use in LED devices,” Abolhasani says.

NC State has filed a provisional patent covering NanoRobo and is open to exploring potential market applications for the technology.