Drawing No. EH–MT–012 // Engineering Materials
Gallium Arsenide Properties
Reviewed September 2026
Gallium arsenide is a III-V semiconductor used in high-frequency, optoelectronic and high-efficiency photovoltaic applications. Its elastic and thermal properties are anisotropic/crystal-specific.
Representative properties
The stated basis, temperature and direction are part of the value. Switch units without changing the physical reference.
What changes these properties?
Engineering variability
- Thermal conductivity depends on purity, defects, doping and temperature.
- Single-crystal elastic constants vary with orientation.
- Wafer fracture is controlled by surface damage, edges and processing defects.
- At high temperature arsenic volatility and compound phase equilibrium matter in addition to nominal melting behavior.
Selection note
Used for RF electronics, lasers/LEDs, solar cells and optoelectronics where high electron mobility/direct bandgap outweigh brittleness and material cost.
Where a property is shown as qualitative rather than numeric, that is intentional: the selected source or the material physics does not justify a single comparable scalar.
Gallium arsenide in practice
Specified where silicon physically cannot do the job — direct-bandgap light emission and very high frequency — and nowhere else, because it is difficult and expensive.
Where it is specified
Optoelectronics: LEDs, laser diodes (including the VCSELs behind optical interconnects and phone face recognition), and photodetectors. GaAs has a direct bandgap, so an electron-hole recombination emits a photon efficiently — silicon, being indirect, essentially cannot make light.
High-frequency electronics: RF power amplifiers in handsets, radar, satellite communications and millimetre-wave front ends, where electron mobility roughly five times silicon's allows operation into the tens of gigahertz.
Space photovoltaics: multi-junction GaAs cells exceed 30% efficiency and tolerate radiation far better than silicon, which is why satellite arrays use them despite the cost.
Chosen over what
Against silicon: much higher mobility, direct bandgap, semi-insulating substrates that reduce parasitic capacitance, and better radiation tolerance. Against that: far more expensive, mechanically fragile, no native oxide, poor thermal conductivity (about a third of silicon) and limited wafer size.
Against gallium nitride: GaN has a wider bandgap and higher breakdown field and has taken over high-power RF and fast-charging power conversion. GaAs remains preferred for lower-voltage, high-linearity handset amplifiers and for near-infrared optoelectronics.
Against indium phosphide: InP suits the 1.3–1.55 µm telecom windows; GaAs covers shorter wavelengths and is cheaper.
How it fails
Mechanical fragility. GaAs is markedly more brittle than silicon and cleaves easily, so wafers break during handling and thinning, and yield suffers — a significant part of the cost difference.
Poor thermal conductivity makes heat extraction the limiting factor in power amplifiers, forcing careful die attach, thinned substrates and sometimes flip-chip mounting.
No stable native oxide. Unlike silicon, GaAs has no useful passivation layer, so surface states pin the Fermi level and MOSFET-style devices are difficult; the technology relies on MESFETs and HEMTs instead.
Toxicity. Arsenic compounds are highly toxic and volatile at process temperatures; handling, etching and disposal are regulated, which adds real cost.
Fabrication notes
Epitaxy is the core process. Devices are built in layers grown by MOCVD or MBE on the substrate, with lattice matching to AlGaAs a key advantage — AlGaAs can be grown on GaAs with almost no strain, enabling the heterostructures that make quantum-well lasers and HEMTs work.
Substrate growth is by liquid-encapsulated Czochralski or vertical gradient freeze; arsenic's high vapour pressure at the melting point makes this considerably harder than growing silicon.
Semi-insulating substrates are available, which is a genuine advantage for RF: it reduces substrate coupling and loss in a way bulk silicon cannot match.
Wafer sizes remain small — typically 150 mm against silicon's 300 mm — which limits throughput and keeps cost high.
Specifications and standards
SEMI standards for compound semiconductor wafers; ASTM F26 and F76 for Hall measurement and resistivity; JEDEC JESD22 for device qualification; RoHS and REACH restrictions relevant to arsenic content.
References
Sze and Ng, Physics of Semiconductor Devices; Schubert, Light-Emitting Diodes; Freescale/NXP and Qorvo GaAs process technical literature.
How to interpret this material
Stiffness
Young’s modulus describes elastic stiffness. For crystals and composites, orientation can make one scalar modulus only a directional reference.
Strength / failure
Ductile metals can use yield and tensile strength. Brittle ceramics/semiconductors and anisotropic composites require fracture, flexural or directional strength descriptions instead.
Thermal response
Conductivity, heat capacity and expansion are temperature dependent. The last column is a melting or transition descriptor only where that physical concept is appropriate.
Technical sources
The database favors manufacturer, industry, government or academic technical references and labels secondary condition-specific datasets when a primary source does not expose a complete property set.