Single crystalline high-purity germanium bars grown by the zone-refining technique

A novel low-temperature-gradient zone-refining setup is presented here which allows for single crystalline zone-refining of high-purity Ge. The reported single crystalline zone-refined Ge bar has a length of 680 mm and shows a high structural quality, as confirmed by X-ray diffraction techniques. The dislocation density determined by an etch pit density analysis lies between 103 and 104 cm−2. The Ge bar has a net charge carrier density down to 4.7⋅1011 cm−3 with a charge carrier mobility of over 3⋅104 cm2V−1s−1 and a charge carrier lifetime of over 50μs. Hence, the crystals produced by this method are comparable to the quality that can be achieved by the Czochralski method, and the exhibited quality is the highest reported quality that has been achieved by zone-refining so far.