Ohmic contacts for high power LEDs

Abstract

We report novel metallization schemes of transparent p-ohmic contacts for conventional LEDs and reflective p-ohmic contacts for flip-chip and vertical-structure LEDs. Thermally stable and low-resistivity Ru/Ni/ITO ohmic contacts on p-type GaN resulted in the low contact resistivity of 2 x 10 -4 Ω cm 2 and the high transmittance of 92% at 470 nm wavelength. The light output power of the LED with the Ru/Ni/ITO p-contact was increased by 50% compared to the LED of a Ni/Au transparent p-contact. Using a newly developed Ni/Ag/Ru/Ni/Au reflective p-ohmic contact, the low contact resistivity of 5 x 10 -5 Ω cm 2 could be achieved. The light reflectance of the contact was as high as 90% at 470 nm wavelength.