Updated May 25, 2007

GaAs is the semiconductor that spawned the entire MMIC industry. In addition to it's great semiconductor properties, it is also an excellent substrate for microwaves because its resistivity is so high (much higher than even "high resistivity" silicon). GaAs wafers are usually referred to as semi-insulating. GaAs also has very low loss tangent.

This data came from various sources including TriQuint and Avago. Some of this info came from Russia's Ioffe Institute.

Formula or Composition:	GaAs
Dielectric Constant ():	12.88
Dissipation Factor (a.k.a. loss tangent, or tan ):	0.0004
Temperature Coefficient of :	6.8 ppm/°C
Bulk Resistivity:	>10E5 Ohm-cm
Temperature Coefficient of Resistivity (TCR):	ppm/°C
Mass Density:	5.32 gr/cc
Specific Heat:	0.33 J/g/°C
Thermal Conductivity (k):	55 W/m°C
Temperature Coefficient of Expansion (TCE):	5.7 ppm/°C
Melting Point	1238°C 2260 °F