GaAs (GaAs)

GaAs is the chemical formula for gallium arsenide, a III-V compound semiconductor with an electron mobility roughly six times higher than silicon. This makes GaAs the material of choice for high-frequency microchips (mobile phone power amplifiers, satellite communication ICs, radar transceivers), high-efficiency multi-junction solar cells used in spacecraft, and red, infrared, and high-brightness LEDs.

Composition and hazard profile: Each GaAs wafer is roughly 51% arsenic and 49% gallium by mass. Arsenic in its elemental and oxidised forms is classified as a Group 1 human carcinogen by the IARC, and gallium-arsenide dust is a recognised respiratory carcinogen. Crushed or pulverised GaAs releases respirable particles of arsenic trioxide on exposure to moisture and air. This is why intact GaAs chips can be handled safely in dismantling, but any thermal treatment, abrasive cutting, or wet milling demands sealed enclosures, HEPA filtration, and respiratory PPE rated for arsenic.

Where GaAs appears in e-waste: Power-amplifier modules inside every 4G and 5G handset (typically 2-4 mm2 of GaAs die per phone), small-outline RF transistors on telecom infrastructure boards, high-brightness LED indicator chips on industrial PCBs, and aerospace solar panels. Quantities are tiny per device but the gallium content alone (about $300 per kg of pure gallium at recent prices) makes recovery economically attractive once volumes exceed 50 kg per month of mixed RF-chip scrap.

Recovery and regulation: India's E-Waste (Management) Rules, 2022, classify GaAs-containing components as hazardous fractions requiring channelisation to a CPCB-authorised recycler with hazardous-waste authorisation. The recovery route is hydrometallurgical — controlled chlorination dissolves gallium and arsenic into a leach liquor, after which gallium is recovered by electrolysis and arsenic is precipitated as a stable trisulfide for safe disposal. See /glossary/hydrometallurgy for the broader leaching framework.