Thermal Stability and Phase Transformation of Conductive $\alpha$-$(\mathrm{Al}_{x}\mathrm{Ga}_{1-x})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ Heterostructures on Sapphire Substrates

TL;DR

This study investigates the thermal stability and phase transformations of fluorine-doped conductive $ ext{Al}_x ext{Ga}_{1-x} ext{O}_3$/Ga$_2$O$_3$ heterostructures on sapphire, revealing stability up to 550°C and providing insights into their structural evolution.

Contribution

It provides the first detailed analysis of the high-temperature phase stability and transformation behaviors of fluorine-doped $ ext{Al}_x ext{Ga}_{1-x} ext{O}_3$/Ga$_2$O$_3$ heterostructures on sapphire substrates.

Findings

Heterostructures are thermally stable up to approximately 550°C.

Phase transformations occur beyond 550°C, affecting material properties.

Achieved high Hall mobility and electron concentration in the heterostructures.

Abstract

Thermal stability and phase transformation of conductive $\alpha$-$(\mathrm{Al}_{0.16}\mathrm{Ga}_{0.84})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ 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 $\alpha$-$(\mathrm{Al}_{0.16}\mathrm{Ga}_{0.84})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ heterostructures with fluorine (F) doping were grown by mist chemical vapor deposition on sapphire substrates, achieving a Hall mobility of $28~\mathrm{cm^{2}\,V^{-1}\,s^{-1}}$ and an electron concentration of $1.4\times10^{20}~\mathrm{cm^{-3}}$. The heterostructures exhibited thermal stability up to approximately $550$--$