Comparison of SiC to other Semiconductors

	Here are some particular noteworthy SiC properties in comparsion to those of GaAs and Si.
		The data are mostly form Cree Inc.
		6H-SiC 4H-SiC GaAs Si Comments Bandgap [eV] 3.03 direct 1.4 direct 1.12 indirect SiC devices can operate at rather high temperatures without suffering from intrinsic conduction effects because of the wide energy bandgap. SiC can also emit and detect short wavelength light which makes the fabrication of blue light emitting diodes and nearly solar blind UV photodetectors possible. Breakdown Electric Field [MV/cm] (for 1000 V operation) 2.4 x 106 0.3 x 106 0.2 x 106 SiC can withstand a voltage gradient (or electric field) over eight times greater than than Si or GaAs without undergoing avalanche breakdown. This high breakdown electric field enables the fabrication of very high-voltage, high-power devices such as diodes, power transitors, power thyristors and surge suppressors, as well as high power microwave devices. Additionally, it allows the devices to be placed very close together, providing high device packing density for integrated circuits. Thermal Conductivity @ RT [W/cm · K] 3.0-3.8 4.9 0.5 1.5 SiC is an excellent thermal conductor; at room temperature, SiC has a higher thermal conductivity than any metal. This property enables SiC devices to operate at extremely high power levels and still dissipate the large amounts of excess heat generated. Saturated Electron Drift Velocity @ E ³ 2 x 105 V/cm) [cm/sec] 2.0 x 107 1.0 x 107 1.0 x 107 SiC devices can operate at high frequencies (RF and microwave) because of the high saturated electron drift velocity of SiC.
	The "Saturated Electron Drift Velocity" is a property that we have not dealt with so far. It is easy to understand - the name tells it all:
		The relation between mobility µ, drift velocity vD, and electrical field E was vD = µ · E. However, for ever increasing fields, the direct proportionality fails, and vD becomes saturated, i.e. does no longer increase with increasing electrical fields.
		The mobility µ then is no longer a useful quantity; we use the saturation electron/hole drift velocity instead. Of course, the maximum speed of devices operated at high field strengths is directly related to this quantity. That is where SiC has the advantage; simply comparing mobilities puts SiC at an disadvantage.

	Cree concludes: "The physical and electronic properties of SiC make it the foremost semiconductor material for short wavelength optoelectronic, high temperature, radiation resistant, and high-power/high-frequency electronic devices.radiation resistant".
		Note that a new property not contained in the table above sort of creeps in: SiC, or more to the point, SiC devices are radiation resistant. Moreover (as mentioned elsewhere), they are "rugged", i.e. they can take a lot of mechanical abuse.
		To put it less euphemistic : SiC devices may still work if something (inluding atomic bombs) explodes nearby; in satellites of all kinds, possibly exposed to lots of radiation etc. By now you get the point: SiC is of tremendous interest to the military!

With frame

10.1.1 Silicon Carbide - Material Aspects

2.2.2 Doping and Carrier Density

© H. Föll (Semiconductors - Script)