Table . Comparison of properties between single, polycrystalline, and amorphous Si.

Single-crystal
Poly-crystal
Amorphous Si
Atomic properties
Atomic number
14
Electron Shells
1s22s22p63s23p2
Radius of Si atom
1.18 Å
Structure
Cubic, diamond
Densest planes of Si atoms
{111} planes
Common Ions
Si4+, Si4-
Atomic density
(atoms/cm3)
4.96 x 1022

Bond angle of adjacent atoms

109 °
Deviation of bond angles
±10° of ideal crystalline Si bond angle
Deviation of bond lengths
±2% of ideal crystalline Si bond length
Density at 300K (g/cm3)
2.329
Atomic weight
28.09 g/g-mol
Lattice spacing (a0 ) at 300K
0.54311 nm
Number of atoms in 1 cm3
4.995 x 1022
Distance between two neighboring atoms
2.35 Å
Atoms per unit cell
8
Space Group
Fd-3m
Heavy hole mass
0.49    
Light hole mass
0.16    
Defect density
    10-15 cm-1 for a-Si:H-10 at.%
Longitudinal electron mass (mL)
0.916    
Transverse electron mass (mL)
0.19    

Radiative recombination coefficient (cm3s−1)

1.1 × 10−14
Mechanical properties

Piezoresistive coefficient

n-Si: p11 = -102
p-Si: p44 = +138
Gauge factor of 90
Gauge factor of 30 - 50

Fracture strength (GPa)

6

0.8 to 2.84 (undoped)
Residual stress
None
Depending on structure; compressive
Poisson ratio
0.262 maximum for (111)
0.23
Young's modulus (N/m2)
1.90 x 1011 for (111) 1.61 x 1011  
Elastic constant (dyn cm-2)
C11=16.6 ×10−11 at 300 K; C12=6.4 ×10−11 at 300 K; C44=7.96 ×10−11 at 300 K
Thermal properties
Thermal conductivity (W/cm-°C)

1.5-1.57

Smaller for poly-Si films with fine grains and much greater with large grains

Thermal expansion (/°C)

2.3

2-2.7

Specific heat (cal/g-°C)

0.169
Boiling point
2480 °C
Melting temperature
1412 °C
Melt heat (Qm, J-g-1)
337
Critical temperature
4920 °C

Vapor pressure (Pa)

1 at 1,650 °C; 10-6 at 900 °C

Vaporization temperature (Tv, °C)
2355
Vaporization heat (Qv, J-g-1)
1446
Critical pressure (atm)
1450
Coefficient of thermal expansion (CTE) (°C-1)
(2.6 - 4.68) x 10-6 for average between 15-1000 °C; 4.2 x 10-6 at 25 °C; zero at -157 °C; negative at liquid air temperature
Thermal diffusion coefficient (cm2/s)
0.9
Entropy at 298 °K
4.5 cal/mol/°K

Diffusion length

300 nm for a-Si:H-10 at.%
Hole diffusion length
1 µm for a-Si:H-10 at.%
Optical properties
Refractive index
3.42 - 3.44
4.05 at 500 nm; 4.1 at 600 nm; 3.93 after deposition at T < 580 °C; 3.51 after deposition at T > 600 °C
Cathodoluminescence (minimum voltage for excitation)
2400
1600

Photoluminescence peak

1.25 eV for a-Si:H(F)-10 at.% at 77 K
Color
Dark, steel gray for single crystal; Black, six-sided plates for graphitoidal Si;
Transparent or light orange for small crystal (similar to c-Si film);
Dark brown
Absorption coefficient
(cm-1)
5.82 x 106 at 3.5 eV

Pre-exponent conductivity factor (Ω-1-cm-1)

>103 for a-Si:H(F)-10 at.%
Indirect energy gap/Optical band gap Eg (eV)
1.12 at 300 K; 1.17 at 0 K (Minimum indirect Eg)
1.6 at 210 °C; 2.0 at 350 °C.
1.55 for a-Si; 1.68 for a-Si:H,F; 1.7 - 1.8 for a-Si:H-10 at.% at 300 K
Direct energy gap (Γ, eV)
3.5    
Variation of optical band gap with temperature
(eV-K-1)
2x - 4x 10-4

ESR spin density (cm-3)

1015 for a-Si:H(F)-10 at.%
Spin–orbit splitting (eV)
0.044    
Infra-red spectra
    2000/640 cm-1 for a-Si:H(F)-10 at.%

Optical phonon energy (meV)

64
Electrical properties

Conduction band tail slope (meV)

25 for a-Si:H(F)-10 at.%; 30 for a-Si
Conduction band minimum
X    

Valence band tail slope (meV)

40 for a-Si:H(F)-10 at.%; 50 for a-Si

Activation energy (ΔE)

≤0.05 for n-type a-Si:H ~1% addition of PH3 to gas phase; ≤0.05 for p-type a-Si:H ~1% addition of B2H6 to gas phase
0.8 - 0.9 for a-Si:H(F)-10 at.%; 0.2 for n-type a-Si:H ~1% addition of PH3 to gas phase; 0.3 for p-type a-Si:H ~1% addition of B2H6 to gas phase
Urbach energy E0 (meV)
46 for a-Si:H; 48 for a-Si:H,F
Electron affinity
4.05 eV

Density of states
in band gap (cm-3)

1 x 1019 for a-Si; 1 x 1016 for a-Si:H

Density of states at the minimum (cm-3eV-1)

>1015 – 1017 for a-Si:H(F)-10 at.%
Fermi level density of states g (EF) (cm-3eV-1)
1015 for a-Si:H; 1015 for a-Si:H,F
Effective density of states at the conduction band edge (Nc, cm-3eV-1)
2.8 x 1019 at 300 K
1021 for a-Si:H(F)-10 at.%
Effective density of states at the valence band edge (Nv, cm-3eV-1)
1.04 x 1019at 300 K

Extended state mobility: electron (cm2s-1V-1)

>10 for a-Si:H(F)-10 at.%
Extended state mobility: hole (cm2s-1V-1)
~1 for a-Si:H(F)-10 at.%
Hole drift mobility µh
(cm2V-1s-1)
450-600
10-20 for a-Si:H; 10-2 for a-Si:H(F)-10 at.%
Electron drift mobility µe
(cm2V-1s-1)
≤1500
20 - 40
1 for a-Si:H-10 at.%
Intrinsic carrier concentration ni
1.0 x 1010 cm-3
Minority carrier lifetime
2.5 x 10-3 s
8 x 10-11 for grain size 0.2 µm; 7 x 10-6 for grain size 4,000 µm
Intrinsic Debye length
24 µm
Dielectric Constant at 300 K
11.9
Temperature resistivity coefficient (TCR, °C-1)

p-type: 0.0017
Nonlinear; e.g. 0.0012; between negative and positive depending on doping level

Dark conductivity
-1-cm-1)

≥1 for n-type a-Si:H: ~1% addition of PH3 to gas phase; ≥1 for p-type a-Si:H: ~1% addition of B2H6 to gas phase
10-10 for a-Si:H(F)-10 at.% at 300 K; 10-2 for n-type a-Si:H: ~1% addition of PH3 to gas phase; 10-3 for p-type a-Si:H: ~1% addition of B2H6 to gas phase
Electrical resistivity (Ω-cm)
Depending on doping level at room temperature; 2 x 103 at -190°C; (2.3 - 3.2) x 105 at 22 °C; 15 at 300 °C; 0.4 at 500 °C
Strong function of the grain structure of the film; always higher than that of Si single crystals; 4 x 105 for doping level <1015 cm-3;
1011 for undoped a-Si:H-10 at.% at 300 K; 102 for n+ a-Si:H-10 at.% at 300 K; 103 for p+ a-Si:H-10 at.% at 300 K
Breakdown field
3 x 105 V/cm
Electron diffusion constant
34.6 cm2s-1
Hole diffusion constant
12.3 cm2s-1