Silicon carbide crystallizes in numerous (more than 200 ) different modifications
(polylypes). The most important are: cubic unit cell: 3C-SiC (cubic unit cell,
zincblende); 2H-SiC; 4H-SiC; 6H-SiC (hexagonal unit cell,
wurtzile ); 15R-SiC (rhombohedral unit cell). Other polylypes with rhornbohedral
unit cell: 21R-SiC 24R-SiC, 27R-SiC etc.
In all polytypes except 3C- and 2H-Sif atomic layers with cubic
(C) and hexagonal (H) symmetry follow in a regular alternation
in the direction of the c axis. This can be thought of as a nutural one-dimensional
superkmice imposed on the "pure" - i.e. h-layer free 3C-SiC [Dean
et al.(1977)], the period of the superlaltice being different for
different polylypes SiC.
Si-C Polytype | 3C-SiC | 4H-SiC | 6H-SiC | 15R-SiC |
Crystal structure | Zinc blende (cubic) | Wurtzite ( Hexagonal) | Wurtzite ( Hexagonal) | Rhombohedral |
Crystal structure | T2d-F43m | C46v-P63mc | C46v-P63mc | C53v-R3m |
Remarks | Referens | |||
Crystal structure | 3C-SiC | Zinc blende (cubic) | ||
4H-SiC | Wurtzite ( Hexagonal) | |||
6H-SiC | Wurtzite ( Hexagonal) | |||
15R-SiC | Rhombohedral | |||
Group of symmetry | 3C-SiC | T2d-F43m | ||
4H-SiC | C46v-P63mc | |||
6H-SiC | C46v-P63mc | |||
15R-SiC | C53v-R3m | |||
Bulk modulus | 3C-SiC | 2.5 x 1012 dyn cm-2 | 300 K | Goldberg et al.(2001) |
4H-SiC | 2.2 x 1012 dyn cm-2 | |||
6H-SiC | 2.2 x 1012 dyn cm-2 | theoretical estimation 0.97 x 1012 dyn cm-2 (experimental data) |
||
Linear thermal expansion coefficient | 3C-SiC | 2.77 (42) x 10-6 K-1 | Slack & Bartram (1975) | |
Debye temperature | 3C-SiC | 1200 K | Goldberg et al.(2001) | |
4H-SiC | 1300 K | |||
6H-SiC | 1200 K | |||
Melting point | 3C-SiC | 3103 (40) K | p = 35 bar. Peritectic decomposition temperature |
Scace & Slack (1960) |
4H-SiC | 3103 ± 40 K | at 35 atm | Tairov & Tsvetkov (1988) | |
6H-SiC | 3103 ± 40 K | at 35 atm. see also Phase diagram | Tairov & Tsvetkov (1988) | |
Density | 3C-SiC | 3.166 g cm-3 | 293 K | Kern et al. (1969) |
3.21 g cm-3 | 300 K | Harris et al.(1995b) | ||
4H-SiC | 3.211 g cm-3 | 300 K | Gomes de Mesquita (1967) | |
6H-SiC | 3.21 g cm-3 | 300 K | Harris et al.(1995b) | |
Hardness | 3C-SiC, 4H-SiC 6H-SiC |
9.2-9.3 | on the Mohs scale | Goldberg et al.(2001) |
Surface microhardness | 3C-SiC, 4H-SiC 6H-SiC |
2900-3100 kg mm-2 | 300 K, using Knoop's pyramid test |
Kern et al. (1969), Shaffer (1965) |
Dielectric constant (static) | 3C-SiC | ε0 ~= 9.72 | 300 K | Patric & Choyke (1970) |
4H-SiC | The value of 6H-SiC dielectric constant is usually used |
300 K | ||
Dielectric constant (static, ordinary direction) |
6H-SiC | ε0,ort ~= 9.66 | 300 K | Patric & Choyke (1970) |
Dielectric constant (static, extraordinary direction) |
6H-SiC | ε0, || ~= 10.03 | 300 K | Patric & Choyke (1970) |
Ratio between the static dielectric constant (ordinary and extraordinary direction) |
6H-SiC | ε0,ort / ε0, || ~= 0.9631 | 300 K | |
Dielectric constant (high frequency) | 3C-SiC | 6.52 | 300 K | Patric & Choyke (1970) |
4H-SiC | The value of 6H-SiC dielectric constant is usually used |
300 K | ||
Dielectric constant (high frequency, ordinary direction) |
6H-SiC | εort ~= 6.52 | 300 K | Patric & Choyke (1970) |
Dielectric constant (high frequency, extraordinary direction) |
6H-SiC | ε || ~= 6.70 | 300 K | Patric & Choyke (1970) |
Infrared refractive index | 3C-SiC | ~=2.55 | 300 K | Goldberg et al.(2001) |
4H-SiC | ~=2.55 (c axis) ~=2.59 ( ||c axis) |
300 K | Goldberg et al.(2001) | |
6H-SiC | ~=2.55 (c axis) ~=2.59 ( ||c axis) |
300 K | Goldberg et al.(2001) | |
Refractive index n(λ) | 3C-SiC | n(λ)~= 2.55378 + 3.417 x 104·λ-2 | 300K, 467nm < λ< 691nm | Shaffer & Naum (1969) |
4H-SiC | n0(λ)~= 2.5610 + 3.4 x 104·λ-2
ne(λ)~= 2.6041 + 3.75 x 104·λ-2 |
300K, 467nm < λ< 691nm | Shaffer & Naum (1971) | |
6H-SiC | n0(λ)~= 2.55531 + 3.34 x 104·λ-2
ne(λ)~= 2.5852 + 3.68 x 104·λ-2 |
300K, 467nm < λ< 691nm | Shaffer & Naum (1971) | |
also see Refractive index n vs. wavelength and photon energy | Shaffer & Naum (1971) | |||
Radiative recombination coefficient | 4H-SiC 6H-SiC |
1.5 x 10-12 cm3/s | 300 K, estimation | Galeskas et al. (1997) |
Optical photon energy | 3C-SiC | 102.8 meV | 300 K | Goldberg et al.(2001) |
4H-SiC | 104.2 meV | |||
6H-SiC | 104.2 meV | |||
Effective electron mass (longitudinal)ml |
3C-SiC | 0.68mo | 300 K | Son et al.
(1994); Son et al. (1995) |
3C-SiC | 0.677(15)mo | 45K, Cyclotrone resonance | Kaplan et al. (1985) | |
4H-SiC | 0.29mo | 300 K | Son et al.
(1994); Son et al. (1995) |
|
6H-SiC | 0.20mo | 300 K | Son et al. (1994); Son et al. (1995) | |
Effective electron mass (transverse)mt |
3C-SiC | 0.25mo | 300 K | Son et al. (1994); Son et al. (1995) |
3C-SiC | 0.247(11)mo | 45K, Cyclotrone resonance | Kaplan et al. (1985) | |
4H-SiC | 0.42mo | 300 K | Son et al. (1994); Son et al. (1995) |
|
6H-SiC | 0.42mo | |||
Effective mass of density of states mcd | 3C-SiC | 0.72mo | 300 K | Son et al. (1994); Son et al. (1995) |
4H-SiC | 0.77mo | |||
6H-SiC | 2.34mo | |||
Effective mass of the density of states in one valley of conduction band mc |
3C-SiC | 0.35mo | 300 K | Son et al. (1994); Son et al. (1995) |
4H-SiC | 0.37mo | |||
6H-SiC | 0.71mo | |||
Effective mass of conductivity mcc | 3C-SiC | 0.32mo | 300 K | Son et al. (1994); Son et al. (1995) |
4H-SiC | 0.36mo | |||
6H-SiC | 0.57mo | |||
Remarks | Referens | |||
Effective hall mass of density of state mv | 3C-SiC | 0.6 mo | 300 K | Son et al. (1994); Son et al. (1995) |
4H-SiC | ~1.0 mo | 300 K | ||
6H-SiC | ~1.0 mo | 300 K | ||
Lattice constant, | 3C-SiC | a=4.3596 A | 297 K, Debye-Scherrer; see also Temperature dependence |
Taylor & Jones (1960) |
4H-SiC | a = 3.0730 A b = 10.053 |
300 K | Goldberg et al.(2001) | |
6H-SiC | a = 3.0730 A b = 10.053 |
297 K, Debye-Scherrer; see also Temperature dependence |
Taylor & Jones (1960) |