Beneath the gate oxide is the channel that's made from gallium arsenide. As current flows, electrons move along the channel, between the source and the drain. For this reason, the channel is known as the transistor's active region, and it must have a smooth, defect-free interface with the gate oxide layer to operate properly. That's because the gate oxide acts as an insulator by protecting the channel from the electrode. Otherwise, a short circuit would occur. .
For more than 30 years, researchers have been trying to make gallium arsenide-based gate oxides. Two years ago, also at IEDM, Bell Labs researchers announced the first gallium arsenide MOSFET by precisely depositing the gate oxide - atomic layer by atomic layer - on the channel surface, using a process known as molecular beam epitaxy. .
In the latest research, the researchers have improved the stability and electrical characteristics of the gate oxide, comprised of gallium oxide and gadolinium oxide. As a result, the current decreases only 1.5 percent after 150 hours of operation under extreme conditions. In contrast, the previously best research results reported a 22 percent drop over a three-hour period. "After we further improve the gate oxide material, gallium arsenide MOSFET devices may be very attractive for various applications, such as cellular phones, wireless base stations and potentially microprocessors in computers," said researcher Ming-Hwei Hong of Bell Labs, which is the research and development arm of Lucent Technologies. .
Currently, most wireless applications use gallium arsenide metal-semiconductor field-effect transistors (MOSFETs), which lack a gate oxide, but which are necessary because higher frequencies are attainable with gallium arsenide compared to silicon. (That's because electrons can travel five to six times faster in gallium arsenide-based transistors.) However, because the insulating gate oxide layer is not present, the current always is on, and cellular phones and base stations require two voltage sources.
(Hennessey Interview) As Kevin Hennessey explains, he works with epitaxlly grown Gallium Arsenide with Indium quantum dots. He takes a substrate wafer of Gallium Arsenide and in a chamber there are connected MBE heads which are controlled to emit different elements. ...
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Over the past several years, temperatures around the world kept rising. Sometimes it's unbearable for people on this planet. "The temperature during an eight-day heat wave in Chicago in July 1995 hovered around 100 degrees Fahrenheit. High levels of humidity made the air feel even hotter, creating an almost unbearable and, ultimately, fatal environment. 556 number of deaths was attributed to the heat, which struck the elderly" ("Issues and Controversies: Global Warming "). Until human populations soared and began burning fossil fuels, greenhouse gases remained in relative balance. ...
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