Recent interest in Germanium single crystals with a specifically tailored defect structure is fueled by basic research related to the search of the neutrinoless double-beta decay to unravel the nature of the neutrino. The Leibniz-Institut für Kristallzüchtung (IKZ) is part of the LEGEND collaboration - which is the worldwide leading 76Ge-based double-beta decay experimental program - and conducts research to improve the processing of enriched Germanium.
Kevin-Peter Gradwohl is working in this project and supporting the team within his doctoral thesis on the growth and defect investigation of high-purity germanium crystals. These single crystals have been grown by the Czochralski method in [211] and [110] direction for the purpose of dislocation structure engineering. By growing a thin crystal neck at high growth speed, it was possible to align dislocation types and line directions, since exclusively one of the {111} slip planes is parallel to the growth directions. White beam X-ray topography was utilized to carry out an extensive Burgers vector analysis, which revealed that the dislocations are primarily of screw and 60°- type in the [211] and [110] crystal, respectively. These results were correlated with the charge carrier lifetimes of the crystals.
Mr. Gradwohl studied materials science and has been working on a doctoral thesis on "Growth and defect investigation of high-purity germanium crystals for radiation detector applications" at the IKZ since 2018. The native Austrian completed both his Master's and Bachelor's degree with honours. Already during his studies, Kevin-Peter Gradwohl specialised in the growth and characterisation of crystals within the exchange programme with Northwestern Polytechnical University (Xi´an China) as well as in numerous internships.
The award will be published in the Journal of Crystal Growth as part of the conference proceedings.
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Kevin-Peter Gradwohl
Radhakrishnan Sumathi
Section Semiconductors
