Silicon (Si) Semiconductors

Topics Covered

Description
Applications
Chemical Properties
Electrical Properties
Thermal, Mechanical and Optical Properties
Safety Information

Description

Silicon is a period 3 element belonging to Block P and Group 14. Its electronic configuration is [Ne]3s2 3p2.

Silicon is available in abundance, second only to oxygen, and seldom occurs as a pure free element naturally. It constitutes 25.7% of the earth’s crust by weight. Silicon is normally found in the form of silicon dioxide or silicates in rocks, minerals and sands.

Single silicon crystals required for semiconductor devices are obtained using the Czochralski process. Silicon is extensively used in integrated circuits, which form the basis of most computers; hence modern technology is almost entirely dependent on it

Applications

Pure monocrystalline silicon finds use in the production of silicon wafers for the semiconductor sector, in high-efficiency and high-cost photovoltaic applications and in electronics.

Pure silicon is an intrinsic semiconductor and conducts electrons and electron holes released by atoms in the crystal on heating. This causes an increase in the electrical conductivity of silicon with increase in temperature.

The conductivity of pure silicon is quite low, hence it is not suitable as a circuit element for electrons and is doped with small amounts of other elements. This doping ensures that the conductivity of silicon is substantially increased and its electrical response is adjusted by controlling the charge and number of activated carriers.

This kind of control is essential for solar cells, transistors, semiconductor detectors and other semiconductor devices that are used in the computer industry and other technical applications. For instance, silicon is used as a continuous wave Raman laser medium to create coherent light in silicon photonics, even though it is not very effective as a constant light source.

Chemical Properties

Chemical Properties
Chemical Formula Si
Molecular Weight 28.08
CAS No. 7440-21-3
IUPAC Name N/A
Group IV
Band Gap 1.12 eV
Band Gap Type Indirect
Crystal Structure Diamond
Symmetry Group Oh7-Fd3m
Lattice Constant 5.431 Å

Electrical Properties

Electrical Properties
Intrinsic Carrier Concentration 1x1010 cm-3
Electron Mobility ≤ 1400 cm2 V-1 s-1
Hole Mobility ≤ 450 cm2 V-1 s-1
Electron Diffusion Coefficient ≤ 36 cm2 s-1
Hole Diffusion Coefficient ≤ 12 cm2 s-1
Electrical Resistivity 3-4 µΩ cm @ 0°C

Thermal, Mechanical and Optical Properties

Mechanical Properties
Melting Point 1414 °C
Density 2.329 g cm-3
Young's Modulus 130-188 GPa
Shear Modulus 51-80 GPa
Bulk Modulus 97.6 GPa
Specific Heat (@ 298 K) 0.75 J g-1 K-1
Thermal Properties
Thermal Conductivity 1.3 W cm-1 °C-1
Thermal Diffusivity 0.8 cm2 s-1
Thermal Expansion Coefficient 2.6x10-6 °C-1
Optical Properties
Refractive Index (589 nm @ 293 K) 3.678
Absorption Coefficient (589 nm @ 293 K) 6.993x102 cm-1
Radiative Recombination Coefficient (@ 300 K) 1.1x10-14 cm3 s-1

Safety Information

Safety Information
GHS Hazard Statements H228 - Flammable solid
Safety Precautions S16 - Keep away from sources of ignition
S33 - Take precautionary measures against static discharges
S36 - Wear suitable protective clothing

Source: AZoM

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