Unraveling Si-doped DX centers in AlGaN-based UVC LEDs through 2D cathodoluminescence mapping.

AlGaN-based UVC LEDs are compact, mercury-free, and cover the full 200-280 nm range, making them ideal for medical, military, and industrial uses. However, their internal quantum efficiency remains low due to defects prevalent in Al-rich group III nitrides. In this study, we introduce a novel approach using 2D cathodoluminescence (CL) to identify defect types, Si-doped DX centers and their distributions in UVC LEDs. Focused ion beam scanning electron microscopy (FIB/SEM) was employed to prepare cross-sectional samples, facilitating electron excitation from the side view to optimize CL signal collection. Energy-dispersive X-ray spectroscopy (EDX) was also utilized for direct visual analysis and detailed compositional examination of the layers. To further investigate structural and optical properties, we applied spherical aberration-corrected transmission electron microscopy (AC-TEM) and atomic-resolution electron energy-loss spectroscopy (EELS). This comprehensive analysis provided direct, visual evidence of Si-doped DX center formation, confirming the spatial correlation between Si dopants and nitrogen vacancies (VN) within the N-AlGaN lattice at atomic resolution. Our findings provide essential insights into the detrimental impact of Si-doped defects on UVC LED performance. This understanding serves as a basis for developing targeted defect engineering and material optimization strategies aimed at enhancing the reliability and efficiency of UVC LEDs.