Working Group Aluminium Nitride - Methods

Growth of AlN bulk single crystals:

  • Preparation of high-purity AlN bulk single crystals with up to 15 mm diameter and 12 mm length, using the sublimation-recondensation (physical vapor transport, PVT) technique in inductively heated reactors at growth temperatures above 2000°C in N2 atmosphere (300-900 mbar)
  • Preparation of particularly doped AlN bulk crystals and solid solutions, using various methods for dopant addition
  • Preparation of TaC-based crucible materials by cold isostatic pressing and sintering
  • Numerical modeling of the PVT growth process to optimize thermal gradients and mass transport in the crucible, using the software VirtualReactor
  • Thermodynamic calculations and experiments to test and select proper set-up materials (in collaboration with the group Chemical & Thermodynamic Analysis)
  • Preparation of AlN surfaces for use as seeds in PVT growth, and chemo-mechanical polishing (CMP) to produce substrates with epi-ready surface finish (in collaboration with the group Crystal Machining)
  • Design and construction of AlN growth reactors and reactor components (in collaboration with the group Plant Engineering & Construction)

Characterization of AlN bulk single crystals and substrates (in collaboration with the department of Simulation & Characterization)

  • Structural characterization by optical microscopy, electron microscopy, and X-ray methods and analysis, as well as by atomic force microscopy and defect-selective etching
  • Chemical analysis to investigate impurity and dopant incorporation by EDS, XRF, and ICP-OES (in-house) as well as by SIMS and inert gas fusion (external),
  • Evaluation of the influence of impurities and dopants in AlN crystals using spectroscopic and electrical methods and analysis, e.g. optical absorption, FTIR, EPR, cathode- and photoluminescence, temperature-dependent conductivity, and impedance

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