Characterising the composition, defect concentrations and optical properties of semiconductor alloys based on gallium oxide (Ga2O3)

Beta-phase gallium oxide (beta-Ga2O3) is attracting significant interest for use in electronic and photonic devices, particularly for applications in power electronics where its ultra-wide bandgap (approaching 5 eV) is advantageous. As well as the large bandgap, its high transmission of visible light (~ 90%) makes Ga2O3 a leading contender for UV optoelectronics applications such as solar-blind photodetectors and scintillators. The chance to alloy Ga2O3 with elements such as tin (Sn), indium (In) or aluminium (Al) adds to the potential, bringing in possibilities to tune the bandgap and enhance performance. For example, photodetectors made from tin gallium oxide (TGO) have been shown to outperform Ga2O3 devices by more than one order of magnitude in device response to UV light.
The project will characterise Ga2O3 and related alloys using a combination of advanced materials analysis techniques. An electron microprobe will be used to measure composition, using wavelength dispersive X-ray analysis, and optical emission, using cathodoluminescence, with high spatial resolution (down to approximately 100 nm). For more insulating samples an environmental scanning electron microscope will be used to measure the CL alongside energy dispersive X-ray analysis. Correlating the spatially resolved optical data with the compositional information from the same area will provide an understanding of the properties of the various Ga2O3 alloy systems as well as information on the impact of defects on the material performance. Measuring samples before and after annealing in various atmospheres will be used to identify which defects are present and how their concentrations can be controlled.