Aluminium Gallium Arsenide Semiconductors

Topics Covered

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

Description

Aluminium gallium arsenide AlxGa1-xAs) is a semiconductor material having almost the same lattice constant as gallium arsenide but a bigger bandgap. The x in the formula is a number between 0 and 1 indicating an alloy between gallium arsenide and aluminium arsenide.

The bangap is in the range 1.42 eV (GaAs) to 2.16 eV (AlAs). The bandgap is direct when x < 0.4.

Applications

The applications of aluminium gallium arsenide are:

  • It is used as a barrier material in GaAs-based heterostructure devices.
  • The electrons are confined to a gallium arsenide region by the AlGaAs layer. An example of this kind of device is a quantum well infrared photodetector (QWIP).
  • It also finds application in 1064 nm (Infra-red) laser diodes.

Chemical Properties

The chemical properties of aluminium gallium arsenide are:

Chemical Properties
Chemical Formula AlGaAs
Group III-V
Band Gap 1.42 – 2.16 eV
Band Gap Type Direct when x<0.4
Crystal Structure Zinc Blende
Symmetry Group TD2-F43m
Lattice Constant 5.6533+0.0078x Å

Electrical Properties

The electrical properties of aluminium gallium arsenide are:

Electrical Properties
Intrinsic Carrier Concentration x=0.1 2.1•105 cm-3
x=0.3 2.1•103 cm-3
x=0.5 2.5•102 cm-3
x=0.8 4.3•101 cm-3
Electron Mobility 02 V -1 s-1
0.452
V-1 s-1
Hole Mobility 370-970x+740x2 cm2 V-1 s-1
Electron Diffusion Coefficient 02/s
0.452/s
Hole Diffusion Coefficient 9.2-24x+18.5x2 cm2/s
Electrical Resistivity x=02/s
0.452/s

Thermal, Mechanical and Optical Properties

The thermal, mechanical and optical properties of aluminum gallium arsenide are:

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 (7.55+0.26x)•1011 dyn cm-2
Specific Heat (@ 298 K) 0.33+0.12x J g-1°C-3
Thermal Properties
Thermal Conductivity 0.55-2.12x+2.48x2 W cm-1 °C-1
Thermal Diffusivity 0.31-1.23x+1.462 cm2s-1
Thermal Expansion Coefficient 2.6x10-6 °C-1
Optical Properties
Infrared Refractive Index (@ 300 K) n=3.3-0.53x+0.09x2

Safety Information

The toxicology of aluminium gallium arsenide has not been investigated completely. The dust may irritate the eyes, skin and lungs.

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