Zone refinement equipment

Zone Refining is a method of purifying germanium by segregating active impurities in the germanium based on their so-called Segregation Coefficient. This is how we produce High Purity Germanium at USD.

Zone Refiner A (ZRA) is used to initially purify raw Ge and head and tail pieces from HPGe single crystals, ZRA, and ZRB. The input materials have an impurity concentration of 1E+12-13 cm^-3 and the output is 4-5E+11 cm^-3. ZRA uses long graphite boats which excel at removing Aluminum impurities, as well as Phosphorous and Gaallium, but contributes some Boron impurities. Middle portions of HPGe ingots produced by ZRA are further processed in ZRB.

Zone Refiner B (ZRB) is used to further purify HPGe from ZRA ingots in addition to relatively pure (but not detector grade) portions of HPGe single crystals. The input materials have an impurity concentration of 4-5E+12-13 cm^-3 and the output is 1-2E+11 cm^-3. ZRB uses quartz boats coated with a layer of carbon smoke which excel at removing Boron impurities, as well as further removing Phosphorous and Gallium. Middle portions of HPGe ingots produced by ZRB are grown into detector grade single crystals using a Crystal Growth Furnace.

Crystal growth furnace

We have two crystal growth furnaces to grow detector grade HPGe single crystals from zone refined HPGe ingots.

X ray orientation

We use this machine to measure the crystal orientation of our HPGe single crystals using this X-Ray Diffraction measurement.

Diamond wire saw

The Diamond Wire Saw is used to cut large bell shaped HPGe single crystals into thinner slices. Thin slices are taken from various locations along the z-axis of the crystal to be measured using the Hall Effect method. If two slices of the crystal are measure to have detector grade imupurity concentrations, mobilites, and resistivity, then the thicker slice in between can be used to fabricate a detector.

Hall effect

The Hall Effect measurement system is used to measure the net carrier concentration (impurity concentration), mobility, and resistivity of our zone refined HPGe and HPGe crystals.

Sputter machine

The Sputtering Machine is used to deposit a thin, even layer of amorphous germanium (a-Ge) and aluminum onto the surface of HPGe to form contacts. This is how HPGe is made into a detector.

Targets:

• Ge
• SiO₂
• Al

E-beam evaporation machine