Research Highlights

Composition and strain of the pseudomorphic α-phase intermediate layer at the Ga₂O₃/Al₂O₃ interface

M. Schowalter, A. Karg, M. Alonso-Orts, J. A. Bich, S. Raghuvansy, M. S. Williams, F. F. Krause, T. Grieb, C. Mahr, T. Mehrtens, P. Vogt, A. RosenauerM. Eickhoff

APL Materials 12 (2024): 091104

https://doi.org/10.1063/5.0226857

We investigate the composition of α-phase intermediate layers at epitaxial Ga2O3/Al2O3 interfaces using high angle annular dark field scanning transmission electron microscopy. Their presence is considered a general phenomenon as they are observed independent of the growth technique [Schewski et al., Appl. Phys. Exp. 8, 011101]. Samples were grown by plasma assisted molecular beam epitaxy using different growth conditions. Almost independent of these, the quantitative evaluation of the measured intensities gave Ga concentrations of ∼25%. We show that the previously published model, based on a pure α-Ga2O3 interlayer, fails if it is adapted to the measured composition. Density functional theory (DFT) computations were used to overcome the approximations made in this model and suggest that a stabilization of the layer is possible due to the low Ga concentration (⁠≤35%) at which the α-phase is the most stable. Our surface model computations suggest an exchange of Ga atoms at the surface with Al atoms from the underlying substrate as a possible formation mechanism.

Composition and strain of the pseudomorphic α-phase intermediate layer at the Ga2O3/Al2O3 interface pic
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