GaAs permittivity

Discussion in 'Physics' started by Tada, Mar 4, 2004.

  1. Tada

    Thread Starter New Member

    Jan 26, 2004
    Damn it,

    what are the permittivities or GaAs at equilibrium temperature, T=300k

    isnt there a table that has the permittivities of different materials at equilibrium
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    :) hi,

    do a google search for permitivity table of different elements. you would likely see it. :)
  3. Dave

    Retired Moderator

    Nov 17, 2003
    I must say I have just done a search on the internet and it returns nothing!

    One publication I found on Gallium Arsenide said εr ≈ 12.5

    That seems a reasonable result for room temperature.
  4. Harlan

    Active Member

    Feb 26, 2004
    I dont know if this would be helpful, but I found this on the web

    "GaAs has a thermal conductivity of 0.55 W/cm-°C, which is about one-third that
    of silicon and one-tenth that of copper. As a consequence, the power handling capacity
    and therefore the packing density of a GaAs integrated circuit is limited by the thermal
    resistance of the substrate. The reliability of GaAs devices is directly related to the
    thermal characteristics of the device design, the mounting technique used for the die, and
    the materials used for that interface.
    The thermal conductivity of GaAs is related to the temperature of the material
    over a wide temperature range and varies approximately as 1/T, where T is the
    temperature in kelvin. However, thermal conductivity can be considered linear over a
    very short temperature range [11].
    The power handling capabilities , reliability, and performance of semiconductor
    devices are directly related to the junction temperature of the device during operation.
    While GaAs has a higher thermal resistivity than silicon, this is somewhat offset by the
    higher band gap of GaAs, allowing higher operating temperatures. Nevertheless, thermal
    considerations are extremely important in device design, packaging, and application."

    The site is here and it is a real long PDF file but may be of interest.
    The excerpt is from Page 22 here.

    Credit of course goes to JPL Publication 96-25
    Sammy Kayali
    Jet Propulsion Laboratory
    George Ponchak
    NASA Lewis Research Center
    Roland Shaw
    Shason Microwave Corporation
    December 15, 1996
    National Aeronautics and
    Space Administration
    Jet Propulsion Laboratory
    California Institute of Technology
    Pasadena, California

    Also I found this site that is the charts from the CRC Handbook and may have some helpful info too;

    Harlan :)
  5. Dave

    Retired Moderator

    Nov 17, 2003
    Good fine Harlan.

    That extract you've shown there is basically demostrating Gallum Arsenides biggest problem as a semiconductor - thermal runaway.

    It heats up considerably with only a modest increase in current, which in turn causes more current flow, which heats the device more and so on, until the device just destroys itself.

    Lucky for us we have Silicon which is thermally more stable as a semiconductor device.