Impact of Plasma Treatment of n-Al_0.87Ga_0.13N:Si Surfaces on V/Al/Ni/Au Contacts in Far-UVC LEDs

We investigated the effect of treating the surface of n-Al _0.87 Ga _0.13 N:Si by O ₂ or SF ₆ plasma on the properties of subsequently deposited and annealed V/Al/Ni/Au contacts. Whereas an O ₂ plasma treatment increases the contact resistivity, an SF ₆ plasma treatment decreases it. The operating voltage of far-UVC LEDs emitting at 233 nm could thus be reduced by 2.2 V for a current of 50 mA. The results underline the detrimental impact of oxygen on the formation of low-resistance contacts on n-AlGaN surfaces with high Al mole fraction.