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Virtual GaN substrates on Si wafers

GaN integration via Oxide Buffers on Si

The IHP virtual substrate project focuses today on the integration of functional GaN layers on the Si material platform via oxide buffer layers by heteroepitaxy [1-6].

In order to achieve single crystalline (0001) oriented GaN films on Si(111) substrates a patented bi-layer buffer is used.  By applying Sc2O3/Y2O3 buffers the 17% lattice mismatch between GaN and Si can be reduced by 50% to about 8% (lattice mismatch between GaN and Sc2O3) GaN/Sc2O3/Y2O3/Si(111) heterostructures are prepared by Molecular Beam Epitaxy (MBE) and characterized by various in-situ and ex-situ techniques.

 

Molecular Beam Epitaxy at IHP: “proof of principle”

A 4” MBE cluster system is installed at IHP Materials Research department. It is composed of separated but in-situ interconnected oxide, SiGe, III-V and UHV-CVD chambers with a number of in-situ characterization tools (various RHEED systems, XPS & UPS). As MBE is a highly flexible research thin film deposition method, it is widely employed in the current GaN project for “proof of principle” studies of innovative materials science approaches. In the course of these studies, special emphasize is devoted to develop a fundamental understanding of the solid state physics of GaN heteroepitaxy processes on innovative oxide buffer approaches on Si(111).

Fig. 6: IHP MBE equipment consisting of the four individual but in-situ connected growth chambers.

Characterization techniques:

 

·        Reflection High Energy Electron Diffraction (RHEED)

·        X-ray Photoelectron Spectroscopy (XPS)

·        Photoluminescence (PL)

·        Laboratory and Synchrotron based X-ray Diffraction

Of special importance for a detailed structure characterization of the prepared heterostructures is the Smart Lab diffractometer from Rigaku. Fig. 7 (a) shows an image of the highly flexible diffractometer set-up which offers suitable geometries for carrying out a wide range of X-ray diffraction studies (Grazing Incidence X-ray diffraction mode, pole figure studies etc).

A core competence of IHP materials scientist is the use of 3rd generation Synchrotron radiation (SR) facilities. Due to the brilliance of SR beams, materials science studies at SR facilities provide unprecedented insights in materials on the nano-scale. Fig. 7 (b) shows a top view on the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). For further details, please consult the internet page: http://www.esrf.eu

 

Fig. 7: Smart Lab diffractometer and ESRF in Grenoble for x-ray diffraction studies.

An overview of the IHP technical infrastructure is furthermore available in the internet under the link:

http://www.ihp-ffo.de/en/services/diagnostics-test.html

http://www.ihp-ffo.de/en/research/materials-research/technical-basis.html

The building and the infrastructure of the IHP were funded by the European Regional Development Fund of the European Union, funds of the Federal Government and also funds of the Federal State of Brandenburg.