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NEC Achieves World's Highest One-chip Power Output with its Semiconductor Power Transistor

Source: NEC Corporation

TOKYO December 4th, 2001 - NEC Corporation (NEC) (NASDAQ: NIPNY) (FTSE: 6701q.l) (TSE: 6701) has successfully developed the world s first one-chip nitride semiconductor power transistor capable of achieving a power transmission output of over 100W. The new powerful chip will be aimed at advancing functionality of next-generation of mobile applications.

The nitride semiconductor power transistor was achieved by adopting a high breakdown heterojunction (note 1) suitable for high voltage operation, and through the development of the 50µm thinned sapphire technology, in which the heat dissipation characteristic of the power transistor is sharply improved. The nitride semiconductor s advanced isothermal heating process was made possible with the introduction of a thermal shunt air bridge electrode.

Through this development, NEC simultaneously was able to miniaturize the next-generation mobile phone base station transmission amplifier by less than one-third, more than double the power output and improve energy savings to less than one-tenth of current levels, making the new semiconductor ideal for microwave power devices.

The main features of the nitride semiconductor:

  • Adoption of gallium nitride (GaN: note 2) and aluminum gallium nitride (AlGaN) of the heterojunction realizing a high bias voltage operation of 40V.
  • Power output has been improved by 3 times through the development of the 50µm thinned sapphire technology.
  • Development of a thermal shunt air bridge electrode that makes possible the isothermal heating process.
  • Attainment of a maximum power output of 113W (pulse operation: 10%duty) at 2GHz by applying 40V to a transistor chip with an experimental total gate width of 32mm. Until now, the world s highest power output coming from a nitride semiconductor power transistor was 51W, achieved by Cree Corporation.

    Background
    In response to the release of 3G next-generation mobile phones the market is screaming for smaller base station transmission amplifiers, higher power, and energy saving functions. Until now, the highest power output levels of 240 - 300W demanded by customers has been achieved by using a gallium arsenide (GaAs) transistor, which combined four chips within one package. However, as demand for higher power output rises, adding further chips to the small 12V GaAs transistor will not only increase the total package size and combined power loss, but also due to the power consumption increase of the supply circuit caused by the increase in bias current, it is expected that it will be very difficult, with this structure, to produce power outputs of over 300W.

    NEC has been striving to advance research and development with the goal of solving this power output hurdle, and today, as a result of this concentrated effort, announced the successful development of world s first one-chip nitride semiconductor power transistor capable of achieving a power transmission output over 100W. Combining four of the new nitride transistor chips in one package will make possible a transmission power output of 400 to 500W, clearly surpassing the current highest output rates.

    NEC believes this development will have an important role to play in meeting the ever growing needs for smaller next-generation mobile phone base station transmission amplifiers, increasing power output and improving energy saving, which are increasingly required as technology advances further into the information society. From now, NEC will concentrate on improving the power output ability and long operation life of the device, accelerating research and development to commercialize within the next 2-3 years.

    The results from this research will be presented at the IEEE IEDM (International Electron Device Meeting) 2001 held in Washington on December 4th.

    Part of this research result was achieved through research conducted on the project for the "Development of Mobile Communications and Nitride Semiconductor Devices Used for Sensing" which was commissioned to NEC from NEDO, a local research-and-development consortium.

    About NEC Corporation NEC Corporation (NASDAQ: NIPNY) (FTSE: 6701q.l) is a leading provider of Internet solutions, dedicated to meeting the specialized needs of its customers in the key computer, network and electron device fields through its three market-focused in-house companies: NEC Solutions, NEC Networks and NEC Electron Devices. NEC Corporation, with its in-house companies, employs more than 150,000 people worldwide and saw net sales of 5,409 billion Yen (approx. US$43 billion) in fiscal year 2000-2001. For further information, please visit the NEC home page at: http://www.nec.com

    *** (note:1) The heterojunction is a bi-layer structure, consisting of two different semiconductor that contact with each other on an atomically smooth interface. In an AlGaN/GaN heterojunction, where AlGaN is formed on a GaN ground layer, and the atomic configuration of AlGaN is strained so as to adjust the bond length of AlGaN to that of GaN, since the original bond length is shorter in AlGaN than in GaN. This strain induces electronic charges at the interface, which form the electron gas (assembly of electrons) close to the interface between AlGaN and GaN. Since density of this electron gas is more than 3 times higher than that formed in the heterojunction using gallium arsenide (GaAs), it contributes to the large current and high power operation of a transistor using the AlGaN/GaN heterojunction. (GaN note: 2) A semiconductor having a large bandgap of 3.4 eV, for use as a high-frequency, high-power device operated at high-temperature and/or high-voltage conditions. This is due to the high breakdown field and a high electron velocity of this material. GaN is also a well-known material for blue LEDs, utilizing its large direct bandgap characteristics.

    NEC Press Contacts:
    In Japan Daniel Mathieson NEC Corporation
    TEL: +81-3-3798-6511
    E-mail:d-mathieson@bu.jp.nec.com In Japan Daniel Mathieson NEC Corporation
    TEL: +81-3-3798-6511
    E-mail:d-mathieson@bu.jp.nec.com
    E-mail: E-mail:d-mathieson@bu.jp.nec.com
    Web site: http://www.nec.com

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