Working Group Aluminium Nitride - Summary
Aluminium nitride (AlN) is considered as the preferential substrate material for AlGaN-based UV-optoelectronic devices (LEDs, lasers, sensors). In order to prepare efficient devices fort the deep-UV range (210-280 nm), in particular, excellent structural quality of the active layers is required. This is currently possible only by depositing the layers on AlN bulk crystal substrates having the same excellent structural quality. AlN bulk crystals have further potential fields of application as direct semiconductors with very high thermal conductivity, e.g. as substrates for high frequency and power devices, and for pressure or temperature sensors working at elevated temperatures (> 800°C).
The group Aluminium Nitride is focused on developing PVT growth technology (see Methods) to prepare AlN bulk crystals and substrates relevant for applications. A key aspect is to provide techniques that are suitable for industrial adoption (Advanced UV for Life). Important fields of activity are the iterative increase of the single-crystal diameter to industrially relevant sizes while maintaining the high structural quality, the further improvement of reproducibility and yield, and the adjustment of desired electrical and optical properties (e.g. high deep-UV transparency) of the crystals by controlling impurity incorporation during crystal growth.
Besides, we investigate the preparation of, particularly doped AlN bulk crystals for high-frequency power electronics and high-temperature sensor technology. Based on numerical modeling, purposeful characterization of the crystals, and collaborations with other research institutes, we are continuously optimizing our experimental conditions and elaborate conclusive models for crystal growth.
Furthermore, the group Aluminium Nitride closely collaborates with industrial partners to develop and establish improved materials for use in the PVT growth set-up, as well as plasma-assisted preparation of AlN sputter targets.
C. Hartmann, J. Wollweber, S. Sintonen, A. Dittmar, L. Kirste, S. Kollowa, K. Irmscher, M. Bickermann
Preparation of Deep UV Transparent AlN Substrates with High Structural Perfection for Optoelectronic Devices.
CRYSTENGCOMM (2016) 3488 - 3497
Growth and Properties of Bulk AlN.
In: M. Kneissl and J. Rass (eds.), III-Nitride Ultraviolet Emitters - Technology and Applications, Springer Series in Materials Science 227, (2016), S. 27 - 46
Martens, F. Mehnke, C. Kuhn, C. Reich, V. Kueller, A. Knauer, C. Netzel, C. Hartmann, J. Wollweber, J. Rass, T. Wernicke, M. Bickermann, M. Weyers, M. Kneissl
Performance Characteristics of UV-C AlGaN Quantum Well Lasers Grown on Sapphire and Bulk AlN Substrates.
IEEE PHOTONIC TECH L 26 (2014) 342 - 345
C. Hartmann, A. Dittmar, J. Wollweber, M. Bickermann
Bulk AlN Growth by Physical Vapour Transport.
SEMICOND SCI TECH 29 (2014) 084002
T. Paskova, M. Bickermann
Vapor Transport Growth of Wide Bandgap Materials.
In: P. Rudolph (ed.), Handbook of Crystal Growth, Bulk Crystal Growth - Basic Technologies, 2nd Edition, Vol. 2a (2014), 209 - 240