Fig. 1. Contact resistivity and voltage evaluated at 0.1  kA/cm2 as a function of the annealing temperature for n-contacts on (a) n‐Al0.75Ga0.25N and on (b) n‐Al0.9Ga0.1N. The insets show the experimental IV curves at an electrode distance of 8 μm for different annealing temperatures.

Fig. 2. Experimental IV curves and contact resistivity evaluated at 0.1  kA/cm2 for n-contacts annealed at 800°C on n‐AlxGa1−xN as a function of the Al mole fraction at an electrode distance of 8 μm.

Fig. 3. HAADF STEM images for n-contacts on (a) n‐Al0.75Ga0.25N and on (b) n‐Al0.9Ga0.1N annealed at 850°C. The inset in (a) shows a magnified image of the M/S interface with a thin interfacial AlN layer. (c) Exemplary EDXS line scan across the M/S interface marked by an arrow in (a) for n‐Al0.75Ga0.25N. The dashed line indicates the M/S position. (d) Exemplary EELS spectra for N-K and O-K edges measured at the M/S interface for n‐Al0.75Ga0.25N and for n‐Al0.9Ga0.1N.

Fig. 4. HRTEM images of the M/S interface for (a) n‐Al0.75Ga0.25N and for (b) n‐Al0.9Ga0.1N annealed at 850°C. The lower images (c)–(f) show the FFTs of the respective marked areas in the HRTEM micrographs. The M/S interface is indicated by dashed lines.

Fig. 5. Experimental LIV, EQE, and WPE curves measured on-wafer for a 0.15 mm2 LED emitting at 232 nm under cw operation. The inset shows the spectral power density at 20 mA.