Gallium nitride (GaN)
A wide band-gap semiconductor that features stronger resistance against breakdowns that can occur due to high voltages, compared to conventional semiconductors based on silicon (Si) or gallium arsenide (GaAs).
 High electron mobility transistor (HEMT)
Invented in 1979 by Takashi Mimura of Fujitsu Laboratories (currently a Fellow at Fujitsu Laboratories), this is a transistor made of compound semiconductors that feature excellent speed and noise characteristics. HEMTs are now widely used in satellite broadcast equipment, mobile phones, GPS navigation systems, broadband wireless access systems, and other core technologies fundamental to an information-driven society.
The radio band from 30 MHz to 30 GHz.
 Millimeter wave
The radio band from 30 GHz to 300 GHz. Not widely used yet compared to the band below 10 GHz.
 Breakdown voltage
The maximum voltage that can be applied across a gate electrode and a drain electrode. Voltages in excess of this will cause the semiconductor to break down.
 Negative voltage
With conventional GaN HEMT transistors, applying negative voltage to the gate enables the density of the electrons just below the gate to be zero, thereby enabling the transistor's electrical current to be turned off.
 Electron density
The number per unit volume of electrons distributed on the GaN side at the interface of GaN and n-type AlGaN. These electrons are referred to as a two-dimensional electron gas. In HEMT transistors, a high electron density enables a high power output.
Fujitsu is a leading provider of IT-based business solutions for the global marketplace. With approximately 160,000 employees supporting customers in 70 countries, Fujitsu combines a worldwide corps of systems and services experts with highly reliable computing and communications products and advanced microelectronics to deliver added value to customers. Headquartered in Tokyo, Fujitsu Limited (TSE:6702) reported consolidated revenues of 5.3 trillion yen (US$53 billion) for the fiscal year ended March 31, 2008. For more information, please see: www.fujitsu.com.
Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited, Fujitsu Laboratories Limited is one of the premier research centers in the world. With a global network of laboratories in Japan, China, the United States and Europe, the organization conducts a wide range of basic and applied research in the areas of Multimedia, Personal Systems, Network, Peripherals, Advanced Materials and Electronic Devices. For more information, please see: http://jp.fujitsu.com/labs/en/
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Date: 10 October, 2008
City: Tokyo and Kawasaki, Japan
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