GaAs permittivity

Thread Starter

Tada

Joined Jan 26, 2004
9
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
 

Dave

Joined Nov 17, 2003
6,970
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.
 

Harlan

Joined Feb 26, 2004
46
Tada:
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.
http://parts.jpl.nasa.gov/mmic/mmic_complete.pdf
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
Editors
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;
http://www.indiana.edu/~cheminfo/crc_xtabs_71-79.html

Harlan :)
 

Dave

Joined Nov 17, 2003
6,970
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.
 
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