Silicon single crystals with ultrahigh purity and crystalline perfection are crucial for demanding applications in power electronics, photonics or basic research. The Float-Zone (FZ) method is particularly suitable for the growth of such crystals. We aim to provide FZ know-how, growth processes and custom-made crystals needed for enabling technologies in trends as e-mobility, smart and renewable energy or for the emerging field of quantum computing.

Our activities include the further development of FZ and related crucible-free growth processes (Pedestal, Silicon Granular Crucible method). For our partners in science and industry, we provide dislocation-free crystals with very high resistivity (>10kΩcm) and purity or targeted doping, e.g. with B, P, Bi, Ga, Al, Sb, Au, N. Our FZ furnaces allow the growth of crystals with a diameter of a few mm up to 200 mm. A special focus lies on the growth of isotopically enriched ²⁸Silicon crystals.

The Czochralski (Cz) group specializes in the growth of group-IV semiconductor crystals, silicon (Si), germanium (Ge) and their related alloys for a wide range of applications in electronics, photonics, plasmonics, thermoelectrics and efficient x-ray and γ-ray monochromators. As a member of the grand international GERDA/LEGEND collaboration, we are also striving to produce ultra-high purity Ge single crystals to be used as radiation detectors in astrophysics studies, in the quest for fundamental understanding of the universe. The focus lies in developing and establishing the whole value-chain process technology under one roof. 

• Single crystal growth of ultra-high-purity Ge (n < 10¹¹ cm^-3), including the reduction of natural GeO₂, isotopically enriched ⁷⁶GeO₂ to Ge and zone-refining of Ge up to 12N
• Growth optimization of heavily-doped (n > 10¹⁸ cm^-3) Ge crystals using novel gas-phase doping technique, for THz Plasmonics applications
• Si, Ge crystals specifically doped with exotic dopants like Magnesium or Bismuth for their carrier dynamic studies with Free-Electron-Lasers
• SiGe mosaic crystals and gradient crystals for synchrotron beam line optics; GeSn and SiGeSn crystals for photonics application

Gallium Arsenide (GaAs) is beside Silicon (Si) the most commonly industrially used semiconductor material and is the one main focus of the group’s work.  Research activities are centered on the improvement and optimization of the  Vertical Gradient Freeze ( VGF) process with simultaneous application of magnetic fields, for example to improve process efficiency.  A critical factor thereby is the precise and predictable control of fluid flow.  A further central point of research is the VGF growth of III-V single crystals with specific characteristics for applications in basic research as well as special industrial applications such as detectors.

• Vertical Gradient Freeze (VGF) growth of III-V single crystals (ø = 4“) using KristMAG^® heater-magnet-modules (HMM)
• Growth and characterization of III-V single crystals with custom specifications for research and industry
• VGF growth process development and optimization
• Realization of feasibility studies related to applications of KristMAG^®  technology
• Study of doping and impurity incorporation into crystals under the influence of external fields such as magnetic and ultrasonic fields