Fig. 1. Cross-sectional BFDB STEM images (<1-100>) of the n-AlGaN epilayer grown on a HTA AlN/Sapphire template. (a, b) and (c, d) are the images without and with SLs, respectively. (a, c) and (b, d) are taken with g = (0002) and (11-20), respectively. For one sample, the images with different g vectors are taken in the same area. The white arrows in (b) and (d) denote the edge dislocations in the HTA AlN/Sapphire template.

Fig. 2. Surface and strain states of the n-AlGaN epilayer grown on a HTA AlN/Sapphire template and structure of the SLs. (a, b) and (c, d) are AFM images (5 μm × 5 μm) and XRD RSMs of the (–105) planes for wafers without/with SLs. (e–h) Cross-sectional HAADF STEM image (<11–20>) of an AlN/AlGaN SLs area and corresponding EDS mappings of N, Al, and Ga elements.

Fig. 3. DUV LED structure grown on a HTA AlN/Sapphire template. (a) Structure diagram of the DUV LED. (b) XRD RSM of the (105) plane of the DUV LED wafer. (c–e) Cross-sectional HAADF STEM images (<11–20>) of the p-AlGaN HIL, MQWs, and EBL (areas 1, 2, and 3 inFig. 3(a)) of the DUV LED, respectively. (f–h) HAADF STEM image (<11–20>) of the DUV LED (area 4 inFig. 3(a)) and corresponding EDS mappings of Al and Ga.

Fig. 4. Performance characterizations of the three DUV LEDs. (a) IV curves. The inset shows the normalized EL spectra at the current of 100 mA. (b) LOP and EQE curves. The inset shows a picture of a typical flip-chip packaged LED. (c) Distance-dependent LPD at the current of 100 mA. The insets show the log-scale graph and measurement geometry.

Fig. 5. Inactivation effects of the DUV LEDs on IAV and SARS-CoV-2. (a) Inactivation efficiency for IAV with an initial titer of 2.3×10⁴ PFUs in 60 μL. The inset shows the results for a higher initial titer of 2.3×10⁵ PFUs in 60 μL. (b) Irradiation time-dependent viral inactivation effects for IAV from 2 to 12 cm. The inset shows the live viral titer after 10 s at 8 and 12 cm. (c) Viral inactivation effects of the 256 nm-LED for IAV in 10 s at 4 cm. The viral titers determined by the ratio of PFUs (bar chart) and log10 reduction (cyan line) are shown. (d) Live viral titer after 10 s irradiation for IAV at 4 cm on different materials. Values are presented as the means±SDs (n=3, n=number of independent replicates). (e) Inactivation efficiency with an initial titer of 2.3×10⁴ PFUs in 60 μL for SARS-CoV-2. Values are presented as the means±SDs (n=2, n=number of biological replicates). (f) Inactivation effects of the 256 nm-LED for different pSARS-CoV-2 variants. BHK21-hACE2 cells are infected for 24 h with pseudo-SARS-CoV-2 irradiated or not, and then, the luciferase activity is measured to reflect the virus entry efficiency. Time-dependent effects at 4 cm are evaluated by measuring the luciferase activity for individual pSARS-CoV-2. The dotted line represents the detection limit. Values are presented as the means±SDs (n=3, n=number of independent replicates). **p<0.01.

Fig. 6. Total relative RNA levels in the cell (a) supernatants and (b) lysates infected by a virus suspension irradiated for 10 s at 4 cm or not after 24 h. The relative RNA level is normalized to that of the mock (non-infected) group. Values are presented as the means±SDs (n=3, n=number of independent replicates). **p < 0.01, ***p < 0.001, ****p < 0.0001.