Toward Ultrawide Bandgap Engineering: Physical Properties of an α‐(TixGa1−x)2O3 Material Library

Due to its high bandgap of 5.3–5.6 eV and high predicted breakdown field of 10 MV cm−1, much attention is drawn to the ultrawide bandgap semiconductor α‐Ga2O3 for applications in high‐power and solar blind optoelectronic devices. In contrast to the thermodynamically most stable β‐phase of Ga2O3, various transition metal sesquioxides with rhombohedral crystal structure and similar lattice constants to α‐Ga2O3 are available for bandgap engineering toward lower bandgap energies. Therefore the material system α‐(TixGa1−x)2O3 in principle offers the possibility to tune the materials bandgap for wavelength selective optoelectronics over an extremely wide range from 5.6 eV (α‐Ga2O3) down to 0.14 eV (α‐Ti2O3). In this work, high‐throughput combinatorial synthesis by pulsed laser deposition is employed to realize a spatially addressable material library covering almost the entire composition range within the ternary (TixGa1−x)yOz solid solution. Phase‐pure growth of (TixGa1−x)2O3 up to x = 0.25 is reported, exceeding previously found miscibility limits by a factor of 5. The physical properties of the material system are investigated in relation to x and bandgap engineering within the rhombohedral α‐(TixGa1−x)2O3 material system is demonstrated over an up to now unprecedented large spectral range from 4.4 to 5.3 eV.