Silicon Carbide Properties


Silicon carbide (SiC) is a Wide bandgap semiconductor that possesses extremely high thermal, chemical, and mechanical stability. SiC is by far the most developed among wide bandgap semiconductors due to the availability of high quality SiC substrates, advances in chemical-vapor-deposition (CVD) growth of epitaxial structures, the ability to easily dope the material n and p type and ability to produce high-quality native oxide. 

SiC has over 170 polytypes. Each of SiC polytypes has different physical properties. The most commonly known polytypes are 3C-SiC, 4H-SiC and 6H-SiC, but only the last two are commercially available. 4H-SiC is preferred for power devices because of its high carrier mobility and its low dopant ionization energy. 


Properties of Some Importmant Semiconductors for Power Devices
Material Bandgap Eg
(eV)
ni
(cm-3)
Electron Mobility
(cm2/V/s)
EC
(MV/cm)
vsat
(107cm/s)
Thermal Conductivity 
(W/cm/K)
Si 1.12 1.5 x 1010 1400 0.3 1.0 1.5
GaN 3.39 1.9 x 10-10 1000 3.3 2.5 1.3
3C-SiC 2.20 6.9 800 2 2.0 5
4H-SiC 3.26 8.2 x 10-9 960 ( // c-axis)
800 ( c-axis)
3 2.0 4.9
6H-SiC 3.00 2.3 x 10-6 400 ( // c-axis)
85 (   c-axis)
3 2.0 4.9
Diamond 5.5 1.6 x 10-27 2200 5.6 2.7 20

Several figures of merit (FOM) have been proposed to quantify the performance improvement with SiC. For unipolar power switching devices, SiC offers more than 500 times improvment over Si. 

Comparsion of normalized figures of merit of SiC and Si
  JFOM KFOM BFOM BHFFOM
Si 1 1 1 1
3C-SiC 280 5.8 140 25
4H-SiC 400 5.1 560 69
6H-SiC 400 5.1 240 29
Note: 
JFOM: Johnson's FOM for high frequency, high power discrete amplifiers;
KFOM: Keyes' FOM for high speed switches;
BFOM: Baliga's FOM for low-frequency, high-power unipolar switches;
BHFFOM: Baliga's FOM for high-frequency, high-power unipolar switches.