how to get high performance transistors?

The Holy Grail for transistor designers has been the requirement to be able to get high performance at reduced costs over very large substrate areas. Transistors on cheap and flexible substrates like glass and plastics are currently unable to deliver such performance and therefore do not lend themselves to seamless monolithic integration of increased electronic functions on human interface devices (displays and sensors).

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At present, high performance transistors are only available in crystalline materials which are expensive and have to be attached ex-situ onto larger area substrates, which adds to the expense and complexity of system design. If both the electronics and display substrates can be integrated onto one platform, it would usher a new dawn in immersive and personal electronics. Individuals will thus be able to communicate, send and receive information of value, and access data about their current environment and health status with freedom, at leisure, and in comfort.

However, in general, the deposition of semiconductor films used to make transistors on such substrates has to be carried out at low temperatures to preserve substrate integrity. As a result, the quality of the organic or inorganic semiconductor films is severely constrained, and has a dramatic influence on the transistor performance.

Engineers now propose the use of clever transistor structure designs to overcome some of the issues with obtaining suitably low power and high speed operations in standard material systems.

In the first collaborative work with Hitachi Central Research Laboratory, Japan, researchers at the Advanced Technology Institute of the University of Surrey have experimentally and theoretically demonstrated that for transistors of disordered silicon films, superior switching performance (low leakage current, and steep sub-threshold slope) can be achieved by making the conduction channel in the transistor very thin. A higher ION/IOFF ratio, which exceeds 1011, can be achieved for devices with a 2.0-nm-thick channel. Another seminal work from the same research laboratory at Surrey, is on the newly developed source-gated transistor (SGT) concept by Professor John Shannon.

Compared to a field-effect transistor, the SGTs can operate with very short source-drain separations even with a thick gate insulator layer to achieve high speed, good stability and superior control of current uniformity, providing a significant advantage in terms of the fabrication process. Dr Xiaojun Guo, one of the lead investigators, comments: "Engineering of the transistor structure itself rather than the channel material can lead to improved device performance. It will enable the design of high-performance large area circuits and systems based on low-cost reliable material processes".

Professor Ravi Silva, Director of the Advanced Technology Institute states: "This work will help extend the already well established CMOS fabrication technologies for use in large area applications such as displays and sensors, which are at the heart of consumer electronics.

The ATI is fortunate that we have been at the forefront of two potential technologies that can lead to enhanced device performance in disordered materials by clever nano-scale structural design of disordered transistors. This type of work sponsored by the EPSRC forms the bedrock for future electronic technologies".

This research will be published in the journal 'Science', and a more detailed version of the nano-designed transistor will appear in 'IEEE Electron Device Letters'.

A cellphone base station in every home

Sprint´s "Airave" femtocell is available in select US cities.

if you've ever had trouble getting a connection for your cellphone in your home, you could soon take matters into your own hands. Instead of relying on an overworked base station, consumers may be able to have their very own base stations inside their homes.

Called "femtocells," these miniature cellphone base stations are designed to be plugged into a home broadband or cable line. Then, they connect your call via the Internet to your service provider´s network, so you pay your Internet provider instead of your cellphone carrier. If you wander away from the short-range, low-power femtocell, your call will be handed over to the local base station, like normal.

The main advantage of a femtocell is, of course, improved coverage. A handful of femtocell companies already exist, and they claim that their technology offers much better clarity than Internet call systems such as VoIP that rely on Wi-Fi, where the signal is easily obstructed.

The new gadgets - femtocells are about the size of a cable box - could have other advantages, too. They could offer a cheap connection for downloading music, video, and podcasts to iPhones and their ilk. Femtocells could also prove valuable with the increasing popularity of 3G phones, whose high-frequency signals suffer from weakening over long distances. And, since femtocells could also have their own SIM cards, they could make calls themselves, such as alerting you when another cell phone enters your home.

However, femtocell makers still have a few challenges to face before the product is ready for market. Most important is the challenge of ensuring that cell phones in the home connect to the femtocell rather than the city´s base station (the "macrocell").

Security is another issue. If femtocells become a feature in every home, the devices will have to adjust their frequencies to avoid interference with neighboring lines.

Finally, the idea of installing a mini base station inside the home will likely concern some individuals, since it´s another source of microwaves. On the other hand, femtocells will allow cell phones to work at reduced power due to their proximity, so there´s a bit of a trade-off.

In February, the Mobile World Congress in Barcelona, Spain, found the technology promising, boosting the hopes of the companies that have invested heavily in femtocell research. For example, companies such as Ubiquisys and ip.access in the UK and Sprint in the US are betting that the advantages of the technology will overcome the challenges. While Sprint is already releasing heavily subsidized $50 femtocells in select US cities, other companies believe more testing is needed, and suggest a final price closer to $250.

Warner backs Sony Blu-ray format

Blu-ray's supporters have been celebrating Warner's decision

Warner Brothers is to release high definition films only in Sony's Blu-ray format, in a blow to rivals in the long-running format war.

Warner was the only major studio still releasing films both in the competing Blu-ray and HD DVD formats.

Five studios now back Blu-ray solely. Only Universal Pictures and Paramount Pictures favour HD DVD.

The backers of HD DVD deny their format is dead but admitted disappointment with the Warner decision.

Consumer choice

Walt Disney, Twentieth Century Fox, Metro-Goldwyn-Mayer and Sony Pictures are the other studios that only release in Blu-ray format.

Both formats deliver high definition pictures and sound and work with HD televisions, but they are not compatible with each other and neither will play on older DVD players.

Warner said it had opted for Blu-ray because 60% of its US high-definition sales last year had been in that format.

Warner Home Video will stop releasing new titles on HD DVD at the end of May.

The announcement forced a swift reaction from the HD DVD Promotional Group.

The organisation cancelled all the meetings it had scheduled with journalists at high profile Consumer Electronics Show (CES) in Las Vegas and called off a press conference booked for Sunday evening.

In a statement the HD DVD group said: ""While Warner's decision is a setback for HD DVD, the consumer has benefited from HD DVD's commitment to quality and affordability - a bar that is critical for the mainstream success of any format.

"We believe widespread adoption of a next generation format will ultimately be determined by the consumer," it added.

'A quick death'

Rich Greenfield at Pali Capital predicted that HD DVD would now "die a quick death" and predicted that would be good news for DVD sales.

Soonl only two studios will release movies in the HD DVD format

"While we still expect overall consumer spending on DVDs to decline at least 3% in 2008, the risk of an even worse 2008 DVD environment has most likely been avoided by Warner's early 2008 decision," he said.

Toshiba, a founding partner of the HD DVD standard, denied that its format was dead, with Akiyo Ozaka, president of Toshiba America Consumer Products saying that HD DVD "has not lost".

"We were very disappointed with Warner Brothers' announcement," he admitted at CES.

But he added: "Sales of HD DVD were very good last year, especially in October to December."

Wireless GPS systems

The new firmware code in the Jupiter 30 xLP and Jupiter 32 xLP improves time-to-first-fix in urban environments, significantly increases navigation sensitivity and provides greater stability

Navman Wireless OEM Solutions has incorporated the low-power SiRF technology into its GPS solutions. The Navman Wireless Jupiter 30 xLP and Jupiter 32 xLP extra low power modules feature the new 65nm SiRFstarIII GSC3e(f)/LPx chipset and offer up to 30% power savings over earlier modules. The Jupiter 30 xLP and Jupiter 32 xLP devices include the new SiRFstarIII GSW 3.2.5 firmware code and Navman software features including: Write-to-Flash for easy configuration storage and retrieval; Ephemeris Push for rapid satellite acquisitions and starts; and user-selectable profiles to maximise operation in a variety of environments.

The new firmware code improves time-to-first-fix in urban environments, significantly increases navigation sensitivity and provides greater stability, including improved response to transient conditions and improved jamming mitigation.

Remote Microscopy

A modular microscope attachment for cell phones could improve the quality of telemedi

Mobile microscopy: A cell phone incorporating a microscope (top) developed at the University of California, Berkeley, can capture and transmit pictures such as this 23x-magnification image of the freshwater crustacean Cyclops (bottom). Researchers hope that the device will allow patients in remote areas to send images of red blood cells and other diagnostic information to medical specialists. Credit: David Breslauer

Researchers at the University of California, Berkeley, have developed a modular, high-magnification microscope attachment for cell phones. The device will enable health workers in remote, rural areas to take high-resolution images of a patient's blood cells using a cell-phone camera, and then transmit the photos to experts at medical centers.

The researchers hope that the innovation will help patients with blood disorders who live far from medical specialists get more accurately diagnosed and treated. "I wanted to make optical design relevant to today," says Daniel Fletcher, a professor of bioengineering at Berkeley. Fletcher's students found it relatively easy to integrate a simple arrangement of lenses with the cell-phone camera and transmit magnified images to a laptop using a Bluetooth attachment to the phone. The work prompted Fletcher to file a patent through the university and try to make a practical microscope. The researchers say that the cameras in late-model phones are capable of capturing all the details that a doctor would need to identify malaria parasites and cancer cells.

"The challenge was to make a low-cost, durable device with a long battery life," says David Breslauer, a graduate student in Fletcher's lab. "As engineers, we initially wanted to make a whiz-bang gadget to take pictures of both skin and blood. But people in the field told us, 'Once it gets too complicated, no one is going to want to use it. Make something simple that just does the task.'"

The total cost of the first prototype, built from off-the-shelf components, was $75. The current version provides its own sample illumination from cheap, low-power LEDs. The device comes in two versions: with a magnification of about 5 times, for taking images of moles and rashes, and with a magnification of about 60 times, for capturing the details of blood cells and parasites. The higher-magnification model--the larger of the two--is roughly the size and shape of a roll of quarters. Both scopes attach to the phone with a modified belt clip.

"Microscopy is still considered the gold standard" for malaria diagnosis, says Katherine Herz, a medical doctor and a fellow in health policy at Stanford University. "If microscopy could be done with portable equipment ... [it] might be adopted far more widely and prove extremely useful."

Fletcher plans to test the microscope cell phone in Uganda this summer. Initially, his lab will make prototypes, but eventually, it plans to hand off the design to a manufacturer. The Blum Center for Developing Economies at Berkeley, which provided initial funding, will help test the device in Kampala. The scheme is to train local personnel and provide them with the necessary equipment to take pictures of patients' blood on special slides, and then phone in the images to specialists who can identify and count malaria parasites.

The researchers also hope to collaborate with a telemedicine program at the University of California, Davis, that serves rural California. Leukemia patients in remote areas could use the microscope cell phone to transmit images for white blood cell counts.

Wireless ways for high-speed file swaps

New wireless personal networks promise ultra-fast data exchange over short distances

Illustration: NICTA



Gigabit wireless: The Gi-Fi integrated wireless transceiver chip developed at the National ICT Research Centre, Australia. —

Move over Wi-Fi, Gi-Fi is here! They are not putting it quite that way, but recent developments hold out the hope that very large video and other files, can be swapped within seconds, by wireless devices operating over a few metres, in largely unused and unlicensed higher frequency bands. First tangible evidence

The first tangible evidence that Gi-Fi (the ‘Gi’ is for gigabit data rates) might be more than just a neat new acronym, came from Australia last week. Researchers at the Victoria Research Laboratory of National Information and Communication Technology Australia Ltd (NICTA), announced that they had developed the world’s first transmitter-receiver integrated on a single chip, operating at 60 GHz and fabricated using the complementary metal oxide semiconductor (CMOS) process. (http://nicta.com.au/news/current )

The chip, just 5 mm per side, has a tiny 1 mm antenna and uses the 60 GHz ‘millimetre-wave’ spectrum — an unlicensed band of 7 GHz between 57 GHZ and 64GHz. NICTA’s CEO David Skellern says the technology will allow the wireless transfer of audio and video files at rates up to 5 gigabits per second… almost ten times faster than what is currently possible. And the fabrication which uses a 130 nanometre CMOS process, may lead eventually to chips priced as low as $10.

There are a number of firsts here: One, developing high frequency radio components in a standard CMOS process rather than in silicon seems to be a major achievement. If the process can be scaled up, it holds out the possibility of low cost, low power chips which are also very high broadband.

To get a feel for the scale of achievement, consider the best we can achieve with today’s incumbent wireless technologies, Wi-Fi ,Wi-MAX or Bluetooth.

WiFi (WLAN, 802.11) operates in the 2.4 GHz band, has transfer rates of between 11 MBPS and 55 MBPS. WiMAX ( 802.16WiMAX) operates in the 2-11 GHz band and achieves data rates of up to 70 MBPS. Bluetooth (802.15Bluetooth) whose operational ranges are comparable to what can be achieved by the Australian Gi-Fi chip, is typically capable of 20 KBPS to 200 KBPS and in its fastest version, peaks at 55 MBPS. Second, this is one of the first practical applications in the band of what is being known as mw-WPAN, that is, millimeter wave Wireless Personal Area Network… or 802.15.3 to give it the correct designation. An IEEE Task Group no. 3C was formed in 2005 to develop this new WPAN alternative which promises to harness a relatively uncrowded, unlicensed band while offering the hope of data rates of at least 1 GBPS and typically 2 GBPS or better. (see entries for Task Group 3C at http://www.ieee802.org/15/ for technical details and future roadmap).

The potential of mw-WPAN for ultra fast data exchange has prompted companies like Intel, LG, Matsushita (Panasonic), NEC, Samsung, SiBEAM, Sony and Toshiba to form WirelessHD, an industry-led effort to define a specification for the next generation wireless digital network interface for consumer electronics products. Specifically, WirelessHD has a stated goal of enabling wireless connectivity for streaming high-definition content between source devices and high-definition displays. ( see http://www.wirelesshd.org ).

In fact the NICTA effort, says its Gigabit Wireless Project leader Prof Stan Skafidas, has been supported by key industry players like IBM, Synopsys, Cadence, Anritsu, Aglent, Microsoft and SUSS MicroTec, so clearly there is industry interest in exploiting any technology that might boost data rates and drop product costs, ten fold… an enticing possibility.

Usable prototypes

In an indoor environment, the NICTA Gi-Fi device ( usable prototypes may be less than a year away) is expected to work over a distance of up to 10 metres… which puts it somewhere between Bluetooth and WiFi, range-wise. What will it do for you and me? Consumers could typically download a high definition movie from a kiosk in a matter of seconds to a music player or smart phone and having got home, could play it on a home theatre system or store it on a home server for future viewing, again within a few seconds.

Maybe, it’s not that premature to say, “WiFi, it’s time to move over, the competition is here!”

Silent, microchip-sized 'fan' has no moving parts, yet produces enough wind to cool a laptop

Dan Schlitz of Thorrn Micro Technologies is one of the developers of a new, solid-state micro-fan. Credit: Dan Schlitz and Vishal Singhal, Thorrn Micro Technologies

Engineers harnessing the same physical property that drives silent household air purifiers have created a miniaturized device that is now ready for testing as a silent, ultra-thin, low-power and low maintenance cooling system for laptop computers and other electronic devices.

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The compact, solid-state fan, developed with support from NSF's Small Business Innovation Research program, is the most powerful and energy efficient fan of its size. It produces three times the flow rate of a typical small mechanical fan and is one-fourth the size.

Dan Schlitz and Vishal Singhal of Thorrn Micro Technologies, Inc., of Marietta, Ga. will present their RSD5 solid-state fan at the 24th Annual Semiconductor Thermal Measurement, Modeling and Management Symposium (Semi-Therm) in San Jose, Calif., on March 17, 2008. The device is the culmination of six years of research that began while the researchers were NSF-supported graduate students at Purdue University.

"The RSD5 is one of the most significant advancements in electronics cooling since heat pipes. It could change the cooling paradigm for mobile electronics," said Singhal.

The RSD5 incorporates a series of live wires that generate a micro-scale plasma (an ion-rich gas that has free electrons that conduct electricity). The wires lie within un-charged conducting plates that are contoured into half-cylindrical shape to partially envelop the wires.

Within the intense electric field that results, ions push neutral air molecules from the wire to the plate, generating a wind. The phenomenon is called corona wind.

"The technology is a breakthrough in the design and development of semiconductors as it brings an elegant and cost effective solution to the heating problems that have plagued the industry," said Juan Figueroa, the NSF SBIR program officer who oversaw the research.

With the breakthrough of the contoured surface, the researchers were able to control the micro-scale discharge to produce maximum airflow without risk of sparks or electrical arcing. As a result, the new device yields a breeze as swift as 2.4 meters per second, as compared to airflows of 0.7 to 1.7 meters per second from larger, mechanical fans.

The contoured platform is a part of the device heat sink, a trick that enabled Schlitz and Singhal to both eliminate some of the device's bulk and increase the effectiveness of the airflow.

"The technology has the power to cool a 25-watt chip with a device smaller than 1 cubic-cm and can someday be integrated into silicon to make self-cooling chips," said Schlitz.

This device is also more dust-tolerant than predecessors. While dust attraction is ideal for living-room-scale fans that that provide both air flow and filtration, debris can be a devastating obstacle when the goal is to cool an electrical component.