Thermal stability of epitaxial α-Ga2O3 and (Al,Ga)2O3 layers on m-plane sapphire

Here, we have explored the thermal stability of alpha-(Al,Ga)(2)O-3 grown by the molecular-beam epitaxy on m-plane sapphire under high-temperature annealing conditions for various Al compositions (i.e., 0%, 46%, and 100%). Though uncapped alpha-Ga2O3 undergoes a structural phase transition to the thermodynamically stable beta-phase at high temperatures, we find that an aluminum oxide cap grown by atomic layer deposition preserves the alpha-phase. Unlike uncapped alpha-Ga2O3, uncapped alpha-(Al,Ga)(2)O-3 at 46% and 100% Al content remain stable at high temperatures. We quantify the evolution of the structural properties of alpha-Ga2O3, alpha-(Al,Ga)(2)O-3, and alpha-Al2O3 and the energy bandgap of alpha-Ga2O3 up to 900 degrees C. Throughout the anneals, the alpha-Ga2O3 capped with aluminum oxide retains its high crystal quality, with no substantial roughening.

Automated summary

The study reveals that an aluminum oxide cap grown by atomic layer deposition can maintain the stability of alpha-(Al,Ga)2O3 under high-temperature conditions, while uncapped alpha-Ga2O3 undergoes a structural phase transition at high temperatures. Additionally, uncapped alpha-(Al,Ga)2O3 with 46% and 100% Al content also remains stable at high temperatures.