Thermal Stability and Phase Transformation of Conductive $\alpha$-$({\mathrm{A}\mathrm{l}}_x{\mathrm{G}\mathrm{a}}_{1-x}{)}_2{\mathrm{O}}_3\mathrm{/}{\mathrm{G}\mathrm{a}}_2{\mathrm{O}}_3$ Heterostructures on Sapphire Substrates

Thermal stability and phase transformation of conductive $\alpha$-$({\mathrm{A}\mathrm{l}}_{0.16}{\mathrm{G}\mathrm{a}}_{0.84}{)}_2{\mathrm{O}}_3\mathrm{/}{\mathrm{G}\mathrm{a}}_2{\mathrm{O}}_3$ heterostructures on sapphire substrates were investigated using in situ high-temperature X-ray diffraction (HT-XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Conductive $\alpha$-$({\mathrm{A}\mathrm{l}}_{0.16}{\mathrm{G}\mathrm{a}}_{0.84}{)}_2{\mathrm{O}}_3\mathrm{/}{\mathrm{G}\mathrm{a}}_2{\mathrm{O}}_3$ heterostructures with fluorine (F) doping were grown by mist chemical vapor deposition on sapphire substrates, achieving a Hall mobility of $28\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ and an electron concentration of $1.4\times {10}^{20}\mathrm{c}{\mathrm{m}}^{-3}$. The heterostructures exhibited thermal stability up to approximately $550$–$