Section Crystals for Electronics

Section Crystalline Materials for Electronics


Our aim is to produce small series of prototype substrates with tailored properties from semiconductor crystals with promising properties and to make these available to research partners to enable innovation in epitaxial and device processes or new applications. This requires not only the optimization of crystal growth and preparation processes with regard to technological capability, but also the development of standardized and efficient characterization methods for each specific material.

Research activities

Monocrystalline aluminium nitride is a promising substrate material for the production of ultraviolet light-emitting diodes (UV LEDs), which are used for disinfection, among other things. We produce AlN substrates with low dislocation densities, high UV transparency and high surface quality which partners can use to develop new devices. The developed processes and technologies will later on be adjusted and optimized for other application-relevant materials.

The section also operates the "Chemical Metrology" and "Crystal Machining" support labs.

Head of Section
Dr. Thomas Straubinger

Dr. Thomas Straubinger

Ph. +49 30 6392 3123


Aluminium Nitride Crystal Growth

Aluminium nitride (AlN) crystals are grown by physical vapor phase transport (PVT) in crucibles of TaC or W and must have low dislocation densities and relevant diameters (1") regardless of the intended application. Prerequisites for the growth of AlN crystals of high crystalline quality are the availability of low-defect seeds, the avoidance of impurity precipitation during heating up and an optimal T-field design (e.g. high T).

Diameter increase is achieved by gradual seed increase in several successive growth runs with suppression of parasitic growth and slow lateral growth using suitable lateral T-gradients. For the application as a substrate for UV emitters (<= 280 nm) a sufficient transparency in the targeted wavelength range is required, which can be adjusted by specifically influencing the concentrations of the main impurities O, C and Si.

Carsten Hartmann, Lucinda Matiwe, Jürgen Wollweber, Ivan Gamov, Klaus Irmscher, Matthias Bickermann, Thomas Straubinger
Favourable growth conditions for the preparation of bulk AlN single crystals by PVT
DOI: 10.1039/c9ce01952a

Carsten Hartmann, Jürgen Wollweber, Sakari Sintonen, Andrea Dittmar, Lutz Kirste, Sandro Kollowa, Klaus Irmscher, Matthias Bickermann
Preparation of deep UV transparent AlN substrates with high structural perfection for optoelectronic devices
DOI: 10.1039/c6ce00622a

Andrea Dittmar, Jürgen Wollweber, Martin Schmidbauer, Detlef Klimm, Carsten Hartmann, Matthias Bickermann,
Physical vapor transport growth of bulk Al1−xScxN single crystals
Journal of Crystal Growth
DOI: 10.1016/j.jcrysgro.2018.07.022

Dr. Thomas Straubinger

Dr. Thomas Straubinger

Ph. +49 30 6392 3123


At the IKZ the installation of a technology-ready processing line for the preparation and characterization of semiconductor substrates with diameters up to 2" is planned. Currently, the IKZ is already able to produce demonstrator substrates (e.g. aluminium nitride) with small diameters and high quality. For the production of prototypes and small series, the machining effort must be reduced and the process reproducibility must be improved.

Central technical or scientific challenges in the production of semiconductor substrates are:

  • Low-loss sawing of crystals with different mechanical properties, especially of brittle materials.
  • Precise orientation of crystals or substrates.
  • Realization of a high structural surface quality through optimal polishing processes.
  • Realization of a high surface purity by avoiding contamination during the machining processes and suitable final cleaning processes.

Dr. Uta Juda

Dr. Uta Juda

Ph. +49 30 6392 3095

Micro-structuring & Transfer

Semiconductor crystals of group III-V (e.g. InP, AlN) are substrate materials of the future for microelectronic, photonic, and opto-mechanical components that find applications in areas such as mobile communication, sensing, medical technology, and automotive. Integrating them into mature Si or sapphire-based technology platforms has the potential to realize cost-effective semiconductor devices with superior properties.

To enable this fundamentally new and future-oriented device generation, we want to develop preparation and transfer processes for integration on Si and other target substrates for III-V bulk crystals grown at the IKZ. Our activities are conducted in close collaboration with the bulk crystal growth (VGF-III-V, Aluminium Nitride Crystal Growth) and Wafering research groups, the IKZ-IRIS joint lab „Layer Transfer" as well as partners specialized in device development.

The R&D activities include:

  • Preparation of InP and AlN single crystals with high crystalline perfection and tailored bulk properties (especially doping) into thin layers or micro-platelets with atomically smooth surfaces and low defect densities in preparation for the transfer.
  • Optimization of the necessary chemical-mechanical polishing processes (surface) and lithography techniques (micro-structuring).
  • Development of methods for characterizing the structural, optical, and electrical properties of the thin layers and micro-platelets.
  • Development of transfer processes for the heterointegration of thin layers and micro-platelets onto Si substrates and other material platforms.
  • Development of device demonstrators in collaboration with external project partners.
  • Investigation of the influence of doping, micro-preparation, and bonding on crystal properties and device parameters.
  • Adaptation and optimization of the developed methods for other application-relevant materials.

Dr. Karoline Stolze

Dr. Karoline Stolze

Ph. +49 30 6392 3121

Chemical Analysis

An important prerequisite for the reliable evaluation of experimental results in crystal growing is the regular measurement of the chemical compositions and impurity concentrations of starting materials and crystals, as well as the measurement of surface impurities on substrate surfaces. Therefore, existing methods are continuously optimized and new methods will be established.

The current focus of the work is on the development of ICP-OES digestion recipes for oxide- and fluoride crystals produced at the institute and by project partners. Technical and scientific challenges include the measurement of Si impurities and the avoidance of HF-based digestion methods. In the medium term, methods for the measurement of light elements (e.g. O and C in AlN source material) and metallic surface impurities (e.g. Fe) should also be established at the institute.

Dr. Andrea Dittmar

Dr. Andrea Dittmar

Ph. +49 30 6392 2849