SKM 2023 – scientific programme

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DS: Fachverband Dünne Schichten

DS 12: Poster

DS 12.3: Poster

Wednesday, March 29, 2023, 17:00–19:00, P3

Strain and Lattice-Relaxation Effects of (Al,Ga)N/GaN Interfaces on 4D-STEM Signals — •Frederik Otto, Laura Niermann, Tore Niermann, and Michael Lehmann — Technical University of Berlin, Berlin, Germany

The immense increase in computation power over the past decades can be attributed to the decreasing size of semiconductor device structures. Preceding this trend, semiconductor research focuses on thin films and their interfaces with the surrounding substrate material.

At these interfaces of heterogeneous device structures, the atomic lattices are strained due to the mismatch of lattice constants of interfacing materials. Scanning-Transmission Electron-Microscopy (STEM) is capable of resolving strain at a nanometer scale, however, investigated specimens must be sufficiently thin to be electron transparent. For such thin specimens, the relaxation of the strained lattice at its surfaces cannot be neglected when measuring strain in an electron microscope.

Here, knowledge about the underlying strain and relaxation effects at the interface of (Al,Ga)N/GaN Quantum Wells (QWs) is obtained by comparing 4D-STEM measurements with simulations. By carefully choosing the experimental parameters, i.e., convergence angle and tilt, features of multiple scattering events are found in the measured diffraction discs perpendicular to the QW structure at every position of a 2D scanned area. These features are evaluated by comparison with corresponding simulations considering a strain field and relaxation effects as obtained from finite element calculations.