High‐Throughput Combinatorial Synthesis of Rhombohedral α‐(Cr _<i>x</i> Ga _{1− <i>x</i>} ) ₂ O ₃ Solid Solutions over the Entire Composition Range

In this work, a novel combinatorial synthesis method, event‐triggered combinatorial PLD (ETC‐PLD), is presented, with which spatially addressable material libraries of (Cr x Ga 1− x ) 2 O 3 extending over the entire composition range on a single substrate are realized. Utilizing spatially resolved measurements techniques, the structural and optical properties of the material system are screened with high experimental throughput. Phase‐pure growth in the rhombohedral α‐phase is confirmed by X‐ray diffraction measurements, and a comparison of the epitaxy on m‐plane and a‐plane sapphire is presented. By spatially resolved spectroscopic ellipsometry measurements, bandgap engineering within the rhombohedral α‐(Cr x Ga 1− x ) 2 O 3 material system is demonstrated over an up to now unprecedented spectral range from 3.2 to 5.3 eV. These results are promising for applications of the material system in wavelength‐selective optoelectronics.