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DS: Fachverband Dünne Schichten

DS 6: Thin Film Properties I

DS 6.6: Talk

Tuesday, March 19, 2024, 11:15–11:30, A 060

Anisotropic strain relaxation in epitaxially constrained α-(Al,Ga)2O3 thin films on a-plane Al2O3 — •Anna Reis, Michael Hanke, Joao Marcelo Lopes, and Achim Trampert — Paul-Drude-Institut, Hausvogteiplatz 5, 10117 Berlin

Over the past two decades Ga2O3 in its thermodynamically stable β-phase has attracted large scientific interest due to its ultra-wide bandgap enabling the implementation of high-power electronic devices. Lately also the metastable trigonal α-phase of Ga2O3 has received growing attention. Being isostructural to α-Al2O3 ternary (Al,Ga)2O3 can be alloyed across the full compositional range allowing for bandgap engineering between 5.3 eV and 8.8 eV. In order to effectively design heterostructure devices detailed knowledge about strain formation and relief is of fundamental interest.

Thin α-(Al,Ga)2O3 films were epitaxially grown on lattice-mismatched a-plane Al2O3 via molecular beam epitaxy and probed in-situ by X-ray diffraction at the PHARAO facility at BESSY II. Grazing incidence diffraction patterns of the orthogonal (00.6) and (30.0) lattice planes reveal the in-plane strain dynamics of the interface. In the first monolayers the (Al,Ga)2O3 epilayer is found to be fully pseudomorphic whereas afterwards a partially relaxed layer is formed on top. Within deposition of the first 10-15 nm in-plane compressive strain accumulates preferably along the [100]-direction whilst along [001] strain is relieved exposing the anisotropy of the strain relaxation dynamics [A. Reis et al. Appl. Phys. Lett. 123, 122102 (2023)].

Keywords: In-situ Synchrotron X-ray Diffraction; Strain Measurement; Relaxation Dynamics; Group-III Sesquioxides; Thin Films