Optical Activity and Phase Transformations in γ/β Ga<sub>2</sub>O<sub>3</sub> Bilayers Under Annealing
Alexander Azarov, Augustinas Galeckas, Ildikó Cora, Zsolt Fogarassy, Vishnukanthan Venkatachalapathy, E. V. Monakhov, Andrej Kuznetsov
Abstract
Abstract Gallium oxide (Ga 2 O 3 ) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (γ) film on the top of the monoclinic (β) 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 γ/β Ga 2 O 3 bilayers associated with the epitaxial γ‐to‐β regrowth at the interface at temperatures below 700 °C and a non‐planar γ‐to‐β phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga 2 O 3 , interconnecting the phase transformation kinetics with the evolution of the optical properties.