Low contact resistance of the MWCNTs ohmic contact to p-GaN and its application for high power LED

A low contact resistance electrode for p-GaN was obtained using the metallic multi-wall carbon nanotubes (MWCNTs) as the electrode material. The work function of the metallic MWCNTs was confirmed to be 4.84 eV as large as that of Au, Pd and Ni which are generally used for the p-GaN electrode material. Consequently the specific contact resistance was obtained to be as low as 2×10^-3 Ωcm² by optimizing the GaN surface treatment using hydrochloric acid because of the large work function of the MWCNTs. We also characterized the properties of LEDs using the MWCNTs ohmic contact for p-GaN. Low operation voltage and high optical output power was successfully obtained. Threshold voltage was about 2.7 V, and optical output power was about 0.8 W for the 1×1 mm² size LED chip.