Reducing specific contact resistivity of V/Al/Ti/Au n-electrode on n-AlGaN with Al content over 80% for far-UVC LEDs

Abstract AlGaN-based LEDs with peak wavelength below 240 nm (far-UVC) pose no significant harm to human health, thus highlighting their broader application potential. While, there is a significant Schottky barrier between the n-electrode and Al-rich n-AlGaN, adversely impeding electron injection and resulting in considerable heat generation. Here, we fabricate V-based electrodes of V/Al/Ti/Au on n-AlGaN with Al content over 80% and investigate the relationship between the metal diffusion and contact properties during the high-temperature annealing process. Experiments reveal that decreasing V thickness in the electrode promotes the diffusion of Al towards the surface of n-AlGaN, which facilitates the formation of V N and thus the increase of local electron concentration, resulting in lower specific contact resistivity. Then, increasing the Al thickness inhibits the diffusion of Au to the n-AlGaN surface, suppressing the rise of Schottky barrier. Experimentally, an optimized n-electrode of V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm) on n-Al 0.81 Ga 0.19 N is obtained, realizing an optimal specific contact resistivity of 7.30 × 10 −4 Ω·cm 2 . Based on the optimal n-electrode preparation scheme for Al-rich n-AlGaN, the work voltage of a far-UVC LED with peak wavelength of 233.5 nm is effectively reduced.