Defect Spectroscopy of Ga2O3

Gallium oxide is an emerging ultra-wide bandgap semiconductor that holds enormous promise for devices needed to operate in extreme conditions, including high electric fields, high temperatures and radiation environments. Attributes such as its ~ 4.8 eV bandgap, ease of n-type doping, ability to synthesize AlGaO alloys to enable heterostructure devices, availability of melt-grown large area Ga2O3 substrates, and device figures of merit that theoretically exceed more mature wide bandgap technologies based on SiC and GaN, all contribute to rapid acceleration of research in this area. To date, Ga2O3 materials and devices are being grown using a wide range of epitaxial methods, and identifying point defects that are associated with growth conditions, and discriminating between impurity and native physical sources are key to guiding the advancement of material quality so that Ga2O3 can reach its ultimate properties desired for applications in RF power electronics and UV optoelectronics. This presentation focuses on the ongoing investigation of defect states in the Ga2O3 bandgap using a range of defect spectroscopy methods that enable comprehensive characterization of deep level defects across the entire ~ 4.8 eV bandgap. Deep level optical spectroscopy, deep level transient (thermal) spectroscopy and admittance spectroscopy are applied to Ga2O3 materials and devices grown by MBE, MOCVD, LPCVD and EFG methods to enable a quantitative comparison of how defect introduction varies with growth method. High energy particle radiation is used to distinguish native from impurity-based defect states provides further differentiation regarding physical sources. Identification of which defects contribute to important properties for device transport, such as carrier compenstation and electron mobility, is discussed.