Gallium Arsenide (GaAs) Semiconductors

Topics Covered

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

Description

Gallium arsenide is a type III/V semiconductor, with high electron mobility and a high saturated electron velocity compared to silicon, enabling transistors made of gallium arsenide to function at frequencies over 250 GHz.

Gallium arsenide devices are not sensitive to heat because of their wide band gap. Also, these devices typically have less noise than silicon devices, especially at high operating frequencies.

Applications

The applications of gallium arsenide are listed below:

  • Gallium arsenide can be used to manufacture devices such as monolithic microwave integrated circuits, microwave frequency integrated circuits, infrared light-emitting diodes, solar cells, laser diodes and optical windows.
  • GaAs has a direct band gap unlike many other semiconductors implying it can emit light with high efficiency. Being a direct bandgap material, it is resistant to radiation damage enabling its use in optical windows and space electronics in high power applications.
  • It is also used as an electrical substrate and offers natural isolation between circuits and devices. This makes it suitable for millimeter wave and microwave ICs.
  • Solar cells based on GaAs power the Opportunity and Spirit rovers that are exploring the surface of Mars. A number of solar cars make use of GaAs in solar arrays.
  • GaAs diodes are used to detect X-rays.

Chemical Properties

The chemical properties of gallium arsenide are provided in the table below:

Chemical Properties
Chemical Formula GaAs
Molecular Weight 144.645
CAS No. 1303-00-0
IUPAC Name Gallium Arsenide
Group III-V
Band Gap 1.424 eV
Band Gap Type Direct
Crystal Structure Zinc Blende
Symmetry Group Td2-F43m
Lattice Constant 5.4505 Å

Electrical Properties

The electrical properties of gallium arsenide are provided in the table below:

Electrical Properties
Intrinsic Carrier Concentration 1.79 x 106 cm-3
Electron Mobility ≤ 8500 cm2 V-1 s-1
Hole Mobility ≤ 400 cm2 V-1 s-1
Electron Diffusion Coefficient ≤ 200 cm2 s-1
Hole Diffusion Coefficient ≤ 10 cm2 s-1

Thermal, Mechanical and Optical Properties

The thermal, mechanical and optical properties of Gallium Arsenide are provided in the tables below:

Mechanical Properties
Melting Point 1238 °C
Density 5.3176 g cm-3
Young's Modulus 82.68 GPa
Bulk Modulus 75.5 GPa
Thermal Properties
Thermal Conductivity 0.55 W cm-1 °C-1
Thermal Diffusivity 0.31 cm2 s-1
Thermal Expansion Coefficient 5.73x10-6 °C-1
Optical Properties
Refractive Index (589 nm @ 293 K) 3,3
Radiative Recombination Coefficient (@ 300 K) 7x10-10 cm3 s-1

Safety Information

Safety Information
GHS Hazard Statements NA
Hazard Codes T-Toxic
N - dangerous for the environment
Risk Codes R23 - Toxic by inhalation
R25: Toxic if swallowed
R50: Very toxic to aquatic organisms
R53: May cause long-term adverse effects in the aquatic environment
Safety Precautions S 20/21-28-45-60-61

Source: AZoM
 

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