news digest ♦ Telecoms more than 40 percent of the demand in 2016.”
Eric Higham, Director of the Strategy Analytics GaAs and Compound Semiconductor market research service, added, “GaAs-based PAs make up about 95 percent of the market, however W-CDMA PAs fabricated in monolithic CMOS will capture a small but growing share in low-cost 3G devices over the next five years. Even so, the market for GaAs-based PAs will continue to grow in more demanding applications and in the form of complex modules for multiband smartphones.”
GaAs propels NASA with a quantum leap forward in detector technology
A new Thermal Infrared Sensor (TIRS), which incorporates gallium arsenide chips, will take the Earth’s temperature with a new technology that applies quantum physics to detect heat
The TIRS is part of a new Landsat satellite instrument which has arrived at Orbital Sciences in Gilbert, Arizona.
There it will be integrated into the next Landsat satellite, the Landsat Data Continuity Mission (LDCM).
The engineering team at NASA’s Goddard Space Flight Centre in Greenbelt, Maryland, completed TIRS on an accelerated schedule, going from plans on paper to building the instrument in only 43 months.
“That’s a full year ahead of a typical schedule for a new space borne instrument,” says Betsy Forsbacka, TIRS instrument manager.
Aleksandra Bogunovic reaches across the instrument to affix the corners of a Multi-Layer Insulation blanket to the TIRS instrument (Credit: NASA Goddard/Rebecca Roth)
“Two things made this remarkable achievement possible,” says James Irons, LDCM project scientist. “The dedication of the TIRS team working nearly around-the-clock and the use of advanced detector arrays we had on-hand because Goddard played a major role in developing the technology. TIRS will be the first time this technology is used in space.”
TIRS uses Quantum Well Infrared Photodetectors (QWIPs) to detect long wavelengths of light emitted by the Earth with an intensity depending on surface temperature. These wavelengths, called thermal infrared, are well beyond the range of human vision. While devices for thermal infrared night ‘vision’ have long been available, QWIPs offered a new lower- cost alternative to conventional infrared technology. QWIP arrays are designed for sensitivity to specific wavelengths.
The QWIP design operates on the complex principles of quantum mechanics. GaAs semiconductor chips trap electrons in an energy state ‘well’ until the electrons are elevated to a higher state by thermal infrared light of a certain wavelength. The elevated electrons create an electrical signal that can be read out and recorded to create a digital image. The QWIPs’ TIRS uses are sensitive to two thermal infrared wavelength bands, helping it separate the temperature of the Earth’s surface from that of the atmosphere.
TIRS was added to the satellite mission when it became clear that state water resource managers rely on the highly accurate measurements of Earth’s thermal energy obtained by NASA satellites like LDCM’s predecessors, Landsat 5 and Landsat 7, to
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www.compoundsemiconductor.net March 2012
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