Correlation of Multiplicity and Chemistry in Al_xGa_1-xN Heterostructure via Atom Probe Tomography

In this work, the correlation between composition and relative evaporation field was investigated by tracking the statistics of multi-hit detector events in atom probe tomography (APT). This approach is applied systematically to a GaN-based nitride heterostructure with five AlxGa1-xN layers of varying Al composition. The relative field evaporation and the percentage of multi-hit events were found to increase with higher Al concentration. Furthermore, the comparison of the relative evaporation fields of AlN with respect to the constituent ions is found to be less than GaN with respect to its constituent ions. Despite equivalent compositions between opposing interfaces of the same AlxGa1-xN interlayer, the rate of change in multiplicity exhibits a consistent asymmetric trend with a steeper slope across the AlxGa1-xN/GaN interface compared to the GaN/AlxGa1-xN interface. The AlxGa1-xN/GaN heterostructure serves as a test structure for exploring field evaporation and neighborhood chemistry, which can be applied to any material chemistry and particularly other nitride systems.