High Purity Germanium Crystals
The Czochralski crystal-growth method is mainly used for silicon-based electronics and solar energy applications. Umicore has further refined this method in order to make it work for germanium.
Umicore created the world’s purest germanium crystal. With a purity of 99.99999999999% it is used to detect and analyse gamma rays in particle accelerators, nuclear power plants and space applications, such as the Gamma Ray Spectrometer on the Mars Odyssey spacecraft. In 2003 this instrument discovered huge amounts of water across vast areas of Mars. Today, ultrapure germanium crystals are being used to build a giant instrument to detect dark matter in our universe. Umicore continues to innovate and develop its germanium-crystal production technology. This has enabled us to maintain our leadership in germanium substrates for space applications.
The crystals are Czochralski grown in the (100) crystallographic direction. The outer crystal surface is as grown or cylindrically ground (surface roughness max 2,5 μm RMS). The crystal soundness is checked by infrared thermography.
- Transport properties - Hall mobility μH
- p-type μH ≥ 10 000 cm2/V.s (Center measurement)
- n-type μH ≥ 10 000 cm2/V.s (Center measurement)
- Deep levels (measured by DLTS)
- p-type : Cutot ≤ 4,5 109 cm-3
- n-type : Deep level point defects < 5 108 cm-3
- Crystallographic perfection:
|Dislocation density (EPD, cm2)||≤ 10 000||≤ 5 000|
|Lineage (unit length = slice radius)||≤ 4||≤ 3|
|Mosaic structures (unit surface = 10 mm2)||≤ 6||≤ 3|
|Saucers (cm2)||≤ 500||≤ 500|