Optical Activity and Phase Transformations in γ/β Ga2O3 Bilayers Under Annealing

Azarov, Alexander and Galeckas, Augustinas and Cora, Ildikó and Fogarassy, Zsolt and Venkatachalapathy, Vishnukanthan and Monakhov, Eduard and Kuznetsov, Andrej (2024) Optical Activity and Phase Transformations in γ/β Ga2O3 Bilayers Under Annealing. ADVANCED OPTICAL MATERIALS. No. 2401325. ISSN 2195-1071 (In Press)

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Abstract

Gallium oxide (Ga2O3) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (gamma) film on the top of the monoclinic (beta) substrate are fabricated by disorder-induced ordering, known to be a practical way to stack these polymorphs together. Such bilayer structures are annealed to investigate optical properties and phase transformations. Specifically, photoluminescence and diffuse reflectance spectroscopy are combined with transmission electron microscopy, Rutherford backscattering/channeling spectrometry and X-ray diffraction to monitor the evolutions. As a result, a two-stage annealing kinetics is observed in gamma/beta Ga2O3 bilayers associated with the epitaxial gamma-to-beta regrowth at the interface at temperatures below 700 degrees C and a non-planar gamma-to-beta phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga2O3, interconnecting the phase transformation kinetics with the evolution of the optical properties.

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