Electronic Design

From The Labs

Armed with a NASA grant, NanoSciences Corp. will develop a solar-blind, ultraviolet-sensitive photocathode based on III-IV aluminum gallium nitride (AlGaN). Coupling the photodiode with NanoSciences' micromachined silicon microchannel plate and miniature photomultiplier tube technologies should produce high-gain UV detectors that operate at low power and high speed over a large dynamic range. NanoSciences will use molecular beam epitaxy to grow ordered thin-film AlGaN crystals on sapphire substrates, which will be processed into photodiodes. The company will investigate the detector's sensitivity to varying concentrations of aluminum and gallium and to changes in surface conditioning.

A research team headed by Jan Hendrik Schön of Lucent Technologies has discovered what may be the first superconducting organic polymer. According to results reported in Nature magazine, a film known as regioregular poly (3-hexylthiophene) transforms itself from a conventional conductor at room temperature to a superconductor at approximately −270°C. This suggests that organic polymer materials, which can be processed easily, have the potential for use in superconducting applications. Also, the researchers say this work demonstrates that polymers may be tuned across a wide range of electrical conductivity. For details, go to www.nature.com.

University of California researchers have developed a new thermoelectric (TE) cooler that can be grown directly on the chip it's meant to cool. The superlattice microcooler is the result of a collaboration led by John Bowers of UC Santa Barbara and Ali Shakouri of UC Santa Cruz. Compared to conventional TE coolers, which are built separately, the new cooler provides better thermal contact while simplifying manufacturing. The cooler can be as small as 40 mm per side. Researchers believe a single-stage microcooler can drop temperatures by tens of degrees in real-world applications. These findings were reported by the American Institute of Physics in Physics News Update (www.aip.org/physnews/update/).

Scientists in the U.K. may have overcome an existing barrier to optoelectronic integration by crafting an LED from silicon. Nature magazine reports that Kevin Homewood and his colleagues at the University of Surrey created the LED by bombarding a silicon film with boron ions, which in turn produced loop-shaped defects (dislocations) within the silicon. Charge carriers from outside the loops were then brought into and confined within the loops. The prototype LED was nearly as efficient as LEDs made from conventional materials. By allowing a light source to be integrated with silicon circuitry, silicon-based LEDs would enable further miniaturization of the hardware used in optical data transmission. For more information, go to www.nature.com.

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