Compound Semiconductors: Gallium, Indium and Germanium
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Compound semiconductors combine two or more elements to do jobs silicon does poorly: high-frequency radio, lasers, light emission and power conversion. USGS reports that gallium arsenide and gallium nitride wafers feed integrated circuits, which took 73% of U.S. gallium use, and optoelectronic devices, which took 26%; indium phosphide serves 5G fiber-optic networks; and germanium appears in silicon-germanium devices and infrared optics. For defense uses of gallium arsenide and gallium nitride, USGS says no effective substitutes exist.
73% / 26%
U.S. gallium use in integrated circuits and in optoelectronic devices
$120 million
estimated value of U.S. gallium arsenide wafer imports in 2025, against $15 million of gallium metal
99%
of primary low-purity gallium came from China in 2025
Which compound semiconductors depend on critical minerals?
The table links each compound to its minerals, its main uses as USGS describes them, and what can replace it.
| Compound | Minerals | Uses (USGS) | Substitutes (USGS) |
|---|---|---|---|
| Gallium arsenide (GaAs) | Gallium, arsenic | Compound semiconductor wafers for integrated circuits and optoelectronic devices: laser diodes, light-emitting diodes, photodetectors and solar cells. | Silicon CMOS power amplifiers compete in midtier 3G handsets; indium phosphide can replace GaAs infrared laser diodes in some wavelengths; silicon is the principal competitor in solar cells; silicon-germanium is replacing GaAs in some heterojunction bipolar transistors. |
| Gallium nitride (GaN) | Gallium | Integrated circuits and optoelectronic devices used in defense, high-performance computing, telecommunications, aerospace and medical equipment. | No effective substitutes exist for GaAs and GaN in many defense applications. |
| Indium phosphide (InP) | Indium | Substrates for 5G fiber-optic networks; lasers, receivers and high-speed photodetectors for optical communications. USGS expects artificial intelligence to raise demand for specialised chip materials including InP. | USGS names indium phosphide as a substitute for GaAs infrared laser diodes in some wavelengths, and names no substitute for InP substrates. |
| Silicon-germanium (SiGe) | Germanium | Replaces GaAs in some heterojunction bipolar transistors; germane gas is used in certain semiconductor and solar cell manufacturing. | Silicon or gallium arsenide substitute for germanium in certain electronic applications. |
| Indium tin oxide (ITO) | Indium | Conductive coating for flat-panel displays and for data-centre fibers and cables. | Antimony tin oxide, carbon nanotubes, PEDOT, silver or copper nanowires and graphene have been developed as alternatives. |
Source: USGS Mineral Commodity Summaries 2026 chapters on gallium, indium and germanium.
Why can silicon not simply replace them?
Silicon replaces compound semiconductors where cost matters more than performance, and fails where performance matters most. USGS lists silicon-based circuits and solar cells as competitors to gallium arsenide in handsets and photovoltaics, yet says no effective substitutes exist for GaAs and GaN in many defense-related integrated circuits. The pattern runs through the other materials too: indium phosphide and silicon-germanium win in specific wavelengths and speeds, not across the board.
Where do these metals come from?
All three metals are byproducts. Gallium is recovered predominantly from bauxite processing and can be recovered from zinc ores; no primary gallium has been recovered in the United States since 1987. The one New York company that refines high-purity gallium works from imported low-purity metal and new scrap. Supply risk and China's export licensing for gallium, germanium and indium are covered on the export controls and risk page.
Frequently asked questions
What is a compound semiconductor?
A compound semiconductor combines two or more elements, such as gallium and arsenic in gallium arsenide, or indium and phosphorus in indium phosphide. USGS notes they are used in integrated circuits, lasers, light-emitting diodes, photodetectors and solar cells.
What is gallium used for in chips?
Gallium is used as gallium arsenide and gallium nitride to make integrated circuits and optoelectronic devices. In the United States, integrated circuits accounted for 73% of gallium use and optoelectronic devices for 26% in 2025.
Is indium phosphide important for AI and 5G?
USGS says indium phosphide substrates are used in 5G fiber-optic telecommunications networks, and that artificial intelligence is expected to increase demand for specialised chip materials including indium phosphide. It is also used in high-speed photodetectors and laser diodes for optical communications.
Can silicon replace gallium arsenide?
In some uses. Silicon circuits compete with GaAs power amplifiers in midtier 3G handsets and silicon is the principal competitor in solar cells, but USGS says no effective substitutes exist for GaAs and GaN in many defense-related applications.
Sources
Read on October 13, 2026. Figures on this page come from these documents; where a number is an estimate, the source says so.
