Diodes Incorporated (Nasdaq:DIOD), a leading manufacturer and supplier of high quality discrete semiconductors, today announced the release of two new lines of precision Zener diodes. The new Zener lines are the second and third product releases utilizing Diodes-FabTech’s breakthrough precision, high velocity ion implantation process.

Most Zener diode products available on the market today are the result of a traditional diffusion-based process and result in tolerance on Zener breakdown voltage (VZ) down to approximately +/-5% at high yield. In contrast, Diodes’ ion implantation process is highly targeted and enables significant performance improvements with control over VZ tolerance to +/-2% at very high yield and can achieve tolerances down to +/-0.5% if required.

“With these new additions to our Zener line, we continue to leverage our proprietary ion implantation process to push the envelope of device performance and deliver greater value to our customers,” said Mark King. “Zener Diodes are a key component of our sales mix and these new additions mean that we are now able to offer one of the most comprehensive Zener portfolios in the industry.”

The new ultra tight tolerance Zener product line is the DDZ series, and is packaged in a variety of miniature and sub-miniature SOT (3 and 6 pin) & SOD (2 pin) surface mount packages. The series will be marketed as a superior alternative to several popular existing Zener diode lines including the 5200 series, BZT52, and BZX84 series. The DDZ line expands Diodes’ application specific array portfolio, specifically targeting price and space sensitive handheld and battery powered applications requiring no-frills voltage regulation.

The ion implantation technique is also being utilized to produce the new DDZ9600 series featuring a low Zener test current of 50 microAmperes. Optimized for operation at very low biasing currents, the 9600 series is ideally suited for use in portable end products requiring a minimum of power consumption for extended battery life, such as notebooks, mobile communication and hand-held computing devices, including PDAs.

Both the DDZ series and the DDZ9600 series are initially offered in SOD-123, SOT-23, SOD-323, SOT-323 and SOT-363 packages and are assembled at the Diodes-China facility. Initial voltage offerings range from 5.1 Volts to 43 Volts for DDZ and 2.7 Volts to 39 Volts for DDZ9600 with planned expansion down to 3.6 Volts for DDZ and 2.4 Volts for DDZ9600 by 4Q03.

About Diodes Incorporated

Diodes Incorporated (Nasdaq:DIOD) is a leading manufacturer and supplier of high-quality discrete semiconductor products, serving the communications, computer, industrial, consumer electronics and automotive markets. The Company operates three Far East subsidiaries, Diodes-China (QS-9000 and ISO-14001 certified) in Shanghai, Diodes-Taiwan (ISO-9000 certified) in Taipei, and Diodes-Hong Kong. Diodes-China’s manufacturing focus is on subminiature surface-mount devices destined for wireless devices, notebook, flat panel display, digital camera, mobile handset, set top box, DC to DC conversion, and automotive applications, among others. Diodes-Taiwan is our Asia-Pacific sales, logistics and distribution center. Diodes-Hong Kong covers sales warehouse and logistics functions. The Company’s 5″ wafer foundry, Diodes-FabTech (QS-9000 certified), specializes in Schottky products and is located just outside Kansas City, Missouri. The Company’s ISO-9000 corporate sales, marketing, engineering and logistics headquarters is located in Southern California.

Safe Harbor Statement Under the Private Securities Litigation Reform Act of 1995: Any statements set forth above that are not historical facts are forward-looking statements that involve risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements. Potential risks and uncertainties include, but are not limited to, such factors as fluctuations in product demand, the introduction of new products, the Company’s ability to maintain customer and vendor relationships, technological advancements, impact of competitive products and pricing, growth in targeted markets, risks of foreign operations, and other information detailed from time to time in the Company’s filings with the United States Securities and Exchange Commission.

Carbon-composite submounts tipped with diamond are being developed as improved means of dissipating heat generated in high-power laser diodes. Copper is the traditional heat-sinking material for many applications other than laser diodes; it is not suitable for heat-sinking submounts for laser diodes because its coefficient of thermal expansion (CTE) is too high to enable an acceptably close match to the CTEs of laser-diode semiconductor materials. Heretofore, heatsinking submounts for laser diodes have been made from a copper/tungsten alloy, chosen because of its rigidity and its low CTE, which matches the CTEs of the laser-diode semiconductor materials more closely than copper does. Unfortunately, the thermal conductivity of the copper/tungsten alloy is only 45 percent of that of copper. In contrast, the carbon composites of the present development can be made to have both low CTEs and effective thermal conductivities of the order of three times that of copper.

The carbon-composite materials under consideration in the present development effort include, variously, graphitic or vapor-grown carbon fibers in matrices that comprise one or more other forms of carbon and that can include diamondlike carbon. Metals (typically, copper or aluminum) can be used as alternative matrix materials to increase effective thermal conductivities. Like other composite materials, these composites can be formulated to tailor their thermal and mechanical properties within the limits imposed by the intrinsic properties of the constituent materials.

The thermal conductivities of these composites are much higher in the along-fiber directions than in the cross– fiber directions. This anisotropy must be taken into account in designing a heatsinking submount, as in the example illustrated in the figure. The laser diode is mounted on a wedge made of either chemical-vapor-deposited diamond (which has about twice the thermal conductivity of copper) or single-crystal diamond (which has about five times the thermal conductivity of copper). The diamond wedge conducts heat away from the laser diode. The slanted face of the diamond wedge distributes some of the heat to a mating carbon/carbon composite wedge that contains horizontal fibers and that conducts this portion of the heat into a main carbon/carbon heat-sink body that also contains horizontal fibers. The slanted face of the diamond wedge also distributes some of the heat downward into a larger carbon/carbon composite wedge that contains vertical fibers. These vertical fibers meet the horizontal fibers of the main heat-sink body at mating slanted wedge surfaces. The heat-sink body conducts the heat away horizontally. The far end (the right end in the figure) of the heat-sink body is placed in contact with a heat pipe, radiator panel, or other suitable heat sink.

Offering an extremely low EMI, the 8EWF06S and 8EWF12S soft recovery rectifier diodes from International Rectifier are optimised for low forward voltage drop and reverse recovery times of 50 and 80ns.

These 600 and 1200V diodes are offered in a D-Pak with current ratings of up to 8A. The maximum operating junction temperature is 150 degrees C, and each device features glass passivation which ensures high reliability levels and long-term stability.

Link Microtek has launched the LSZ series of zero-bias surface-mount Schottky diodes, which suit use in commercial wireless applications such as up or downconverters and phase detectors.

Made by Microsemi Microwave Products, these microwave discrete semiconductor devices use an SOT-23 plastic package and are supplied taped and reeled ready for mounting by automatic pick and place machines.

The diodes can be specified in a choice of single reverse right or series.

Crydom International has introduced TVS diode protection on its range of SSR products. TVS diodes are fitted internally and shield the entire product. This is said to make the entire process of installing the company’s SSRs easier, as users are not required to fit any extra parts.

With integral shielding the range of SSRs are claimed to be more reliable and help extend the lifespan of the product.

An LED status indication has also been included. This function allows the user to see at a glance whether the SSR is functioning; a green LED displays when power is present at the input.

Charges move more slowly through plastic transistors than they do through transistors based on inorganic semiconductors such as silicon, the stuff of conventional electronics. The new findings indicate that this sluggish rate stems from a ball-and-chain effect: Traveling charges distort the organic materials’ malleable crystal lattices and then have to drag around those distortions.

Such understanding of the fundamental behavior of organic semiconductors is vital to the future of the technology, comments Allen Goldman of the University of Minnesota, Twin Cities.

Some flat-screen computer displays already exploit organic semiconductors as light-emitting pixels. However, the range of future uses is expected to mushroom to include such products as electronic newspapers (SN: 1/31/04,p. 67) and digital gadgetry sewn into clothing (SN: 11/20/99, p. 330).

Researchers have had a tough time getting a clear picture of how charges move in organic semiconductors. That’s because structural defects invariably riddle the thin crystalline films required for making transistors or other devices. Those defects dominate any moving charges’ behavior, thereby blinding researchers to the crystal’s intrinsic contribution to electronic movement.

The Rutgers-Illinois team reports the first organic transistor structure sufficiently free of crystal flaws for the intrinsic behavior of the organic material to stand out. In a yearlong progression of eliminating ever more defects, the researchers have boosted by as much as 200-fold the speed at which charges traverse their transistors.

“That’s definitely an amazing leap ahead,” says Alberto F. Morpurgo of the Delft University of Technology in the Netherlands.

Made of a thick and uniform crystal of the organic chemical rubrene, the structure also has an insulating gap of air instead of a layer of electrically insulating material, which would initiate defects in the crystal. The team, led by Michael E. Gershenson of Rutgers and John A. Rogers of Illinois, describes its work in an upcoming Physical Review Letters.

In their tests, the researchers observed changes in charge speed that theoretical studies and other experimental work have linked to lattice distortions, they say.

The new findings are “technically impressive,” comments Morpurgo. “Two years ago, [attaining] these results would have been considered science fiction,” he says.

Although organic semiconductors will probably never pose a speed challenge to silicon, traits such as their flexibility offer important advantages, Podzorov says. To match those advantages with maximum performance, he notes, researchers must figure out how to eliminate crystal defects in the thin-film components actually used in products.

Taking advantage of quantum effects can greatly speed up such crucial microelectronic components as transistors. For the last decade, scientists have been exploring the possibility of exploiting an electron’s ability to slip through what would apparently be an impenetrable barrier–a quantum phenomenon known as tunneling. Now, researchers have developed an improved tunneling transistor, potentially opening the way for mass production of such devices using conventional manufacturing techniques.

“We have demonstrated real circuits that work and are easily fabricated,” says J.A. Simmons of Sandia National Laboratories in Albuquerque, N.M. He and his coworkers describe their novel device in a report to be published in Applied Physics Letters.

Known as the “double electron layer tunneling transistor,” the device consists essentially of two slabs of gallium arsenide, each 15 nanometers thick, separated by an aluminum gallium arsenide barrier 12.5 nm wide. Electrons in one gallium arsenide layer normally don’t have the energy to traverse the barrier to get into the other layer. However, because the barrier is so thin, electrons, behaving more like waves than particles, can leak through. The tunneling electrons travel extremely rapidly and easily evade atomic impurities and crystal defects that slow down electric charge movement in conventional transistors.

Someday, the very fabric of your shirt might contain flexible electronic devices that monitor your vital signs or enable you to dial in the color or pattern you want to wear that day. Futuristic clothing of this sort may be closer to your closet now that researchers have developed a type of transistor-on-a-fiber.

Josephine B. Lee and Vivek Subramanian of the University of California, Berkeley say that the perpendicular arrangement of a fabric’s fibers should make it possible to wire transistors such as these new fiber ones into sensing devices, wearable displays, and other electronic devices. Conductive wires among the fabric’s threads would provide the transistor-to-transistor links.

Unlike conventional transistor fabrication, which takes place at elevated temperatures and requires high precision and ultraclean conditions, making fiber transistors is “totally compatible with the weaving process,” says Lee. She’s slated to present this new work at an international meeting on electronic devices next month in Washington, DC.

The two researchers make their new transistors by coating hair-thin strands of aluminum with an electrically insulating film. Doing that requires oven temperatures, but the step is completed before weaving takes place. Atop the insulating film, the researchers deposit a layer of pentacene, an organic chemical that behaves as a semiconductor.

In the lab, the researchers have demonstrated another important step in making fiber-based circuits: By positioning threads across the fiber transistors, the Berkeley team can deposit thin films of gold on the fibers except in the tiny areas where the overlying thread masks incoming gold vapor. This process breaks the fibers into discrete transistor regions, each of which can be contacted individually with thin, metallic wires during the weaving process.

“Using the fibers of the textile as shadow masks points to a possibly inexpensive way of making transistors on fabric,” comments Sigurd Wagner of Princeton University. On the other hand, pentacene transistors will require additional protective coatings to prevent degradation by moisture or exposure to the air, he notes.

For tasks such as sensing body temperature, even damaged transistors might work well enough, Lee says. She and Subramanian are now at work on the next step: weaving circuit-laden cloth from the new fibers.

Scientists from US-based Lucent Technologies’ Bell Labs research and development unit report that they have succeeded in fabricating the world’s first individually addressable transistor with a channel that consists of just one molecule.

Last month the same research team unveiled a transistor with a channel - the space between the electrodes where the transistor’s electronic switching and amplification take place - that comprised just a single molecule, but that device could only be fabricated as a matrix of a few thousand molecules that worked in tandem. According to the team the new transistor is a major advance from that, because it can be individually controlled through the channel.

The new transistor is only a billionth of a metre in size - less than a tenth of any transistor produced previously, Bell Labs says, and it is made of an organic semiconductor material containing carbon, hydrogen and sulphur. In addition the transistor can be manufactured without clean room technology.

The Bell Labs scientists believe that these nanotransistors could one day be used in microprocessors and memory chips, enabling thousands of times as many transistors to be squeezed onto each chip than is currently possible.

“This work pushes the miniaturization of electronics to its final frontier,” said Federico Capasso, physics research vice president at Bell Labs. “It may become the cornerstone of a new nanoelectronics era.”

The breakthrough is described in an article published today by the journal Science on their Science Express web site (www.sciencexpress.org).

Scientists have been looking for alternatives to conventional silicon electronics for many years because they anticipate that the continuing miniaturization of silicon-based integrated circuits will peter out in approximately a decade as fundamental physical limits are reached. Some of this research has been aimed at producing molecular-scale transistors, in which single molecules are responsible for the transistor action - switching and amplifying electrical signals.

Bell Labs’ “nanotransistors” - so-called because they are approximately a nanometer, or one-billionth of a meter, in size - appear to rival conventional silicon transistors in performance. They are made using a class of organic (carbon-based) semiconductor material known as thiols. In addition to carbon, thiols contain hydrogen and sulfur.

The main challenges in making nanotransistors are fabricating electrodes that are separated by only a few molecules and attaching electrical contacts to the tiny devices. The Bell Labs researchers were able to overcome these hurdles by using a self-assembly technique and a clever design.

They carved a notch into a silicon wafer and deposited a layer of gold at the bottom to function as one of the transistor’s three electrodes. Then they dipped the wafer into a solution that contained a mixture of thiol molecules and some inert organic molecules, and let it dry. The purpose of adding the inert molecules was to dilute the concentration of thiols. As the solution evaporated from the wafer, a film exactly one molecule thick was left behind on the gold electrode. By carefully adjusting the ratio of the thiol to the inert molecules, the scientists were able to statistically ensure that just one active molecule was present in the area on top of the gold electrode. They then deposited another gold electrode on top of this film, while they built the transistor’s third electrode on one side of the silicon notch.

“It is virtually impossible to attach three electrodes to a microscopically small molecule,” said Bao. “We overcame this problem by letting the molecule find these contacts and attach itself to them, a process called ’self-assembly.’ ”

The chemical self-assembly technique is relatively easy and inexpensive and, unlike silicon, does not require clean room technology.

“Our experiment shows that it is possible to realize transistor action in a single molecule without sophisticated fabrication procedures,” said Schon.

Using two nanotransistors, the Bell Labs scientists built a voltage inverter, a standard electronic circuit module commonly used in computer chips that converts a “0″ to a “1″ or vice versa. Though just a prototype, the success of this simple circuit suggests that nanotransistors could one day be used in microprocessors and memory chips, squeezing thousands of times as many transistors onto each chip than is possible today.

David Goldhaber-Gordon, a professor at Stanford University, commented that the Bell Labs scientists “have achieved several impressive advances toward nanoelectronics. The fabrication technique is particularly elegant in its simplicity.”

Bell Labs has a long and illustrious connection with transistors. William Shockley, John Bardeen and Walter Brattain invented the transistor at Bell Labs in 1947. Their invention spawned the digital age and earned them the Nobel Prize for Physics in 1956. Over the years, Bell Labs scientists have made many of the important contributions that have helped make transistors smaller, faster and more powerful. The technology curve has culminated with the latest development of single-molecule nanotransistors.