Microscopic-scale defect analysis on <b>β</b>-Ga2O3 through microscopy

Abstract

β-Ga2O3 is a wide bandgap semiconductor with potential for surpassing current-generation high-power device performance and cost-effectiveness, due to its unique properties and availability of large high-quality substrates. However, β-Ga2O3 power electronics are still relatively immature, and commercial realization of reliable high-power devices will require intimate knowledge of performance-limiting extended defects. While several defects have been characterized in bulk substrates, less attention has been given to defects in homoepitaxially grown β-Ga2O3, despite its importance in producing high quality active layers for power devices. In this work, we characterize the bulk electronic properties and extended structural defects in (010) β-Ga2O3 homoepitaxially grown via hydride vapor phase epitaxy (HVPE) using photoemission, transmission electron microscopy (TEM), and complementary spectroscopy and microscopy techniques. We observe two types of linear, surface defects aligned along the [001] crystal axis. One defect consists of a micrometer-sized particle and a tail of protruding material, while the other is a groove in the surface. The large particle is a Ga-rich phase that is likely present early in the HVPE growth that disrupts the surface, while the groove defect appears purely structural in nature. Defect etching and TEM analysis reveal that the linear defects are associated with different dislocation structures, which can explain the different local conductivity measured at each. Our results emphasize that proper surface processing of the bulk substrate is still necessary for obtaining higher quality epitaxial growth for large area power devices.