Abstract
Understanding the unique properties of ultra-wide band gap semiconductors requires detailed information about the exact nature of point defects and their role in determining the properties. Here, we report the first direct microscopic observation of an unusual formation of point defect complexes within the atomic scale structure of beta-Ga2O3 using high resolution scanning transmission electron microscopy (STEM). Each complex involves one cation interstitial atom paired with two cation vacancies. These divacancy - interstitial complexes correlate directly with structures obtained by density functional theory, which predicts them to be compensating acceptors in beta-Ga2O3. This prediction is confirmed by a comparison between STEM data and deep level optical spectroscopy results, which reveals that these complexes correspond to a deep trap within the band gap, and that the development of the complexes is facilitated by Sn doping through the increase in vacancy concentration. These findings provide new insight on this emerging material's unique response to the incorporation of impurities that can critically influence their properties.
Highlights
Understanding the unique properties of ultra-wide band gap semiconductors requires detailed information about the exact nature of point defects and their role in determining the properties
This prediction is confirmed by a comparison between scanning transmission electron microscopy (STEM) data and deep level optical spectroscopy results, which reveals that these complexes correspond to a deep trap within the band gap, and that the development of the complexes is facilitated by Sn doping through increased vacancy concentration
Gaining this information is essential to exactly crosslinking theoretical predictions of complexes to measured properties of wide band gap semiconductors, which will provide important guidance to the synthesis and doping of the material with precisely controlled properties
Summary
These DFT results have been utilized in recent β-Ga2O3 defect studies using electron spin resonance [38,39] and infrared spectroscopy [40,41] to attribute the presence of proton irradiation-induced defects and implanted O-H bonds to the same point defect complexes. The reduced intensity of Ga1 columns adjacent to interstitials was substantially more significant than the overall intensity decrease in the area (including the Ga2 columns that are not expected to be involved in the relaxation process) that may be caused by the strain [45] due to the interstitials
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