In 1886 the chemist Clemens Winkler isolated a new element and named it germanium — a quiet discovery that later powered breakthroughs from early transistors to space solar cells.
The uses of germanium today span electronics, optics, energy and precision instruments, even though only small amounts are needed in most devices. Atomic number 32, with a room-temperature semiconductor bandgap around 0.66 eV, germanium’s combination of electronic and optical properties makes it valuable in high-speed chips, fiber-optic cores, infrared optics, satellite solar arrays and radiation detectors.
Electronics and Semiconductors
Germanium’s higher charge-carrier mobilities compared with silicon made it the backbone of the first solid-state devices, and today it’s seeing a comeback in Ge-on-Si integration and photonic detectors. Its practical impacts are faster switching, tighter photonic-electronic integration, and specialized sensors used in communications and defense.
1. Early transistors and diodes — the foundation of solid-state electronics
Germanium was the material behind many of the earliest point-contact and junction transistors in the late 1940s and 1950s. Bell Labs’ transistor research in 1947 relied on germanium devices for practical amplification and switching.
By the 1960s the industry shifted toward silicon largely because silicon tolerates higher operating temperatures, not because germanium lacked utility. Those early germanium components established the era of solid-state electronics and shaped manufacturing and circuit design practices that followed.
2. High-speed electronics and Ge-on-silicon channels
A big reason germanium remains relevant is mobility. Electron mobility in germanium is roughly 3,900 cm²/V·s compared with about 1,400 cm²/V·s in silicon. Hole mobility in Ge is roughly 1,900 cm²/V·s versus about 450 cm²/V·s in Si.
Those numbers translate to faster carriers at a given electric field. Research groups and foundries are experimenting with Ge-on-Si MOSFET channels and strained-Ge approaches to push RF components, low-voltage logic and integrated photonics. The practical result is better performance for wireless front ends and tighter integration between optics and electronics on the same chip.
3. Photodetectors and infrared electronic sensors
Germanium is sensitive to near-infrared wavelengths, which makes it a common choice for photodetectors used in telecommunications and sensing. Ge photodiodes respond well in the 1.3–1.6 µm telecom window used by fiber-optic systems.
That sensitivity is why many fiber-optic receivers and integrated photonics platforms use germanium detectors. The result is faster optical transceivers and denser on-chip optical links inside data centers and telecom equipment.
Optics and Photonics
Germanium’s optical strengths are its transparency across much of the infrared, a high refractive index and compatibility with fiber and wafer processing. Those traits make it useful in fiber cores, infrared lenses and as a substrate for high-efficiency space solar cells.
4. Fiber-optic core doping for telecommunications
Small amounts of germanium dioxide (GeO2) are added to glass preforms to raise the refractive index of fiber cores and control mode propagation. Typical GeO2 concentrations in single-mode cores are a few percent by weight.
This controlled doping enables single-mode operation, predictable dispersion characteristics and low loss over long distances. Those properties underpin long-haul, metro and undersea fiber networks that carry the bulk of modern internet traffic.
5. Infrared optics and thermal imaging lenses
Germanium is a go-to lens material for mid- to long-wave infrared optics because it transmits well roughly from 2 to 14 µm, has a high refractive index and can be machined to optical tolerances.
That makes Ge standard in thermal cameras, night-vision optics, missile seeker windows and non-contact thermometers. Companies such as FLIR Systems commonly use germanium optics in thermal-imaging products, often with anti-reflective coatings to reduce surface reflections.
6. Substrates for high-efficiency space solar cells
Germanium wafers serve as the bottom substrate for multi-junction, space-grade solar cells. Triple-junction cells grown on Ge substrates are widely used on satellites because the substrate supports lattice matching and mechanical stability for the stacked junctions.
Space-grade triple-junction cells commonly exceed 28% efficiency at AM0, and some lab cells by firms such as Spectrolab have passed 30% under test conditions. Those efficiencies deliver reliable power for telecommunications, Earth-observation and deep-space missions.
Scientific and Nuclear Applications
High-purity germanium crystals and specific isotopes of germanium play major roles in precision measurement, nuclear physics experiments and medical isotope production. Their value lies in energy resolution and decay properties useful for both science and clinical logistics.
7. High-purity germanium detectors for gamma spectroscopy and physics
High-purity germanium (HPGe) detectors provide among the best energy resolution available for gamma-ray spectroscopy. For example, HPGe detectors can achieve energy resolution on the order of 0.2% at 1.33 MeV from a Co-60 source, far better than typical scintillator detectors.
That precision matters for environmental monitoring, nuclear safeguards and fundamental physics. Experiments such as GERDA and the Majorana Demonstrator used detectors made from germanium-76 to search for neutrinoless double-beta decay, a sensitive probe of neutrino properties.
8. Medical isotope generators — Ge-68/Ga-68 for PET imaging
Ge-68 decays to Ga-68, and compact Ge-68/Ga-68 generators supply Ga-68 for on-site production of PET radiotracers. Ge-68 has a half-life of about 271 days, so a single generator can provide usable activity for many months.
Those generators improve logistics for PET imaging in oncology and cardiology by reducing dependence on rapid transport from centralized cyclotron facilities. Radiopharmacies use Ga-68 eluates to label tracers used in diagnostic scans.
Industrial, Chemical and Emerging Uses
Beyond electronics and optics, germanium shows up in chemical precursors, specialty glass and niche alloys. Its limited primary production and concentrated supply chains have pushed recycling and secondary recovery to the foreground.
9. Chemical precursors and catalysts in manufacturing
Germanium compounds such as germane (GeH4) and germanium tetrachloride (GeCl4) are common gas-phase precursors for thin-film deposition and epitaxy. Germane is used in MOCVD and CVD processes to grow high-purity germanium or Ge-containing layers.
Germanium-containing catalysts and additives also appear in specialty polymer chemistry and organic synthesis. Note that some precursors like germane are toxic and pyrophoric, so manufacturers handle them with strict safety protocols.
10. Specialty glass, alloys, recycling, and emerging tech
Germanium dioxide finds use in specialty optical glass formulations and in small alloy additions where unique optical or electronic properties are needed. It also appears in scintillators and niche LED applications.
Because primary germanium production is limited, recycling and secondary sourcing matter. Industry recovers germanium from zinc smelter residues, coal fly ash and spent catalysts. Several governments list germanium among critical materials, which is driving more systematic recovery efforts.
On the research side, germanium is part of experimental work on quantum devices and photonic components, which could raise demand if those technologies scale beyond the lab.
Summary
- Small amounts of germanium enable high-value systems: fiber cores, IR optics, space solar cells and precision detectors.
- Germanium’s electronic and optical properties—high carrier mobility and infrared transparency—explain its continued use in specialized semiconductors and sensors.
- Isotopes and HPGe crystals are essential for gamma spectroscopy and PET radiopharmacy logistics.
- Supply constraints have made recycling and secondary recovery important, and ongoing research in photonics and quantum devices could change future demand.
