Suchergebnisse

Understanding the band structure evolution of (AlxGa1x)2O3 alloys is of fundamental importance for developing Ga2O3-based power electronic devices and vacuum ultraviolet super-radiation hard detectors. Here, we report on the bandgap engineering of b-(AlxGa1x)2O3 thin films and the identification of compositionally dependent electronic band structures by a combination of absorption spectra analyses and density functional theory calculations. Single-monoclinic b-phase (AlxGa1x)2O3 (0 x 0.54) films with a preferred (201) orientation were grown by laser molecular beam epitaxy with tunable bandgap ranging from 4.5 to 5.5 eV. The excellent fitting of absorption spectra by the relation of (ah) 1/2 / (h-E) unambiguously identifies that b-(AlxGa1x)2O3 alloys are indirect bandgap semiconductors. Theoretical calculations predict that the indirect nature of b-(AlxGa1x)2O3 becomes more pronounced with increased Al composition due to the increased eigenvalue energy gap between M and U points in the valence band. The experimentally determined indirect bandgap exhibits almost a linear relationship with Al composition, which is consistent with the theoretical calculation and indicates a small bowing effect and a good miscibility. The identification and modulation of (AlxGa1x)2O3 band structures allows rational design of ultra-wide bandgap oxide heterostructures for the applications in power electronics and solar-blind or X-ray detection. ; This research was supported by the National Key Research and Development Project (Grant No. 2017YFB0403003), the National Natural Science Foundation of China (Grant Nos. 61774081, 61322403, and 11227904), the Natural Science Foundation of Jiangsu Province (Grant Nos. BK20130013 and BK20161401), the Six Talent Peaks Project in Jiangsu Province (2014XXRJ001), the Fundamental Research Funds for the Central Universities (021014380093 and 021014380085) and the Australian Research Council. The computational part of this research was undertaken with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government under the NCRIS program.